Which of the following has three, two and one four?
324
22214
3214
3444
Two very smart teenagers, Jane and Gerry, each draw a number from a magician’s hat. They don’t know each other’s numbers, but the magician ensures that the two numbers are positive integers. The magician also informs the teenagers that their numbers are consecutive.
The magician asks them in turn whether they know the other person’s number. After Jane has answered “no” three times, and Gerry has answered “no” three times, Jane then says “yes”.
Which is Gerry's number?
A book costs $1 plus half the price of the sandwich.
The sandwich costs $2 plus half the price of the book.
Which one is more expensive?
The cashier said to a customer:
“You’ve selected 4 books:
‘Rocket Sales’ for $9.99,
‘Math for Dummies’ for $14.99,
‘How to Sell More’ for $19.99, and
‘Marketing in a Bookstore’ for $24.99.
That’ll be $79.96.”
Which of these books should the cashier read?
In one Eastern European country, students receive grades of 2 (fail), 3 (pass), 4 (good), and 5 (excellent).
Peter received 8 grades in mathematics for 8 assignments, the average value of which after rounding was 3 (pass).
What is the smallest possible number of assignments he should redo so that the average score after rounding becomes 5 (excellent)?
John is the best marksman in his county.
What is the smallest number of shots he should fire to be sure that he hits a 4 inch diameter balloon hidden behind a 9x9 inch sheet of paper?
I am thinking of four non-zero integer numbers.
Each number is equal to the product of the other three numbers.
All four numbers are not the same.
What could be the product of the four numbers?
Draw 7 straight lines in a clever way.
What is the largest possible number of vertexes a polygon can have if all of its sides are completely on the 7 lines?
A magician proposed a game to Jane and Gerry.
Each of them is placed in a separate room. In the room, each of them will flip a fair coin, out of sight of the other person. Then each of them must guess what the other person flipped — heads or tails. If they both guess correctly, they will receive a prize.
What is the best strategy?
Three Texans have different first (given) names, different middle names, and different last (family) names.
What is the smallest possible number of names with different spellings they can have?
What is the difference between diameter and radius?
I am between 4 and 6.
I am not 5.
Who or what am I?
Mad Money Bank offers to pay different interest rates depending on the time period. If you do not withdraw your money after a certain period of time, the same conditions will apply in the next period. If you withdraw your money before the deadline, no interest will be paid for the last period.
Martin wants to place $100 million in the bank for 10 months.
Which option is best for him?
Each member of Jane's family drank a cup of tea with milk in the morning. There was no milk or tea left.
Jane drank 1/6 of all milk and 1/8 of all tea.
How many people drank tea with milk in the morning?
Ducats are in use in Mathland country.
The picture shows all the money that Gerry has.
How much money can he spend in the local market today?
Which clock consists of the largest number of moving parts?
A grand piano has three legs, and pedals that do not touch the ground.
Most tables have 4 legs, but a grand piano has only 3 legs.
What is the main reason for that?
The picture shows two flags measuring 4 x 3 meters. Cut the flag on the top into several pieces so that you could stitch them together to make the second flag.
What is the smallest possible number of the pieces?
There is a country whose citizens lose their citizenship when they stop working in the country.
On which continent is this country located?
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Which line has mistakes?
Which is the question nobody can answer with a "yes"?
Is it possible to place fourteen balls in a billiard triangle so that there is no room for the fifteenth ball?
A farmer puts 120 kg of honey into 10 pots, not necessarily equally into each one. He seals the pots, leaves the country, and passes by a border guard who always takes three items in a row for letting people through.
What is the maximum amount of honey the farmer can keep?
Jane has a glass of water, a coin, and 8 wooden toothpicks. The length of each toothpick is less than the diameter of the glass. She wants to place several toothpicks on top of the glass so that they hold the coin in the center of the glass, preventing it from falling into the water.
What is the minimum number of toothpicks needed to do this?
There is a chest buried in each 1x1 meter piece of Square Island's land. One chest contains a treasure, the other 99 chests contain notes indicating the distance to the chest with the treasure.
How many holes do you need to dig to take the treasure with you from the island?
On Hexagon island, sportsmen play billiards on a hexagonal table with 12 pockets located at the corners and in the middle of its sides.
Place several balls on such a table so that each pocket is aligned with at least two balls.
What is the smallest possible number of balls?
Place several balls on a standard 9x4.5 ft billiard table with pockets located at the corners and in the middle of its sides so that each pocket is aligned with at least two balls.
What is the smallest possible number of balls?
Jane is searching for mushrooms in a forest. She starts from a big oak tree and walks 1 meter (m) south, 2 m west, 3 m north, 4 m east, 5 m south, 6 m west, 7 m north, 8 m east, and so on.
After walking a total of 5,000 meters, her basket is full of mushrooms.
How far from the tree is she now?
What is the shape of green quadrilaterals on the chessboard?
You have a standard 297x210 mm piece of paper and no other instruments.
What is the smallest number of times that you fold the paper to trisect (to divide into three equal parts) one of its right angles?
Every day an infection (red squares) spreads among the squares as follows: if a square has two or more infected neighbors, it becomes infected itself. Each square has 4 neighbors via common sides.
Today, 6 squares are infected.
How long will the infection spread?
In a local farm shop, each apple costs the same fixed amount of money.
Jane bought 9 apples for less than $10.
Gerry paid more than $11 for 10 apples.
Why is that?
There are two lines with 3 coins each.
How many coins should you move to make 3 lines with 3 coins each?
Job Interview Question
I made a "horse" from 5 small sticks.
Move just one stick so that the "horse" is rotated and/or flipped, but keeps its original shape.
Which stick do you move?
A pizza has a shape of an ellipse. Its longer diagonal is twice as big as the other diagonal. Jane wants to cut it into 8 pieces of equal area. She has already made two cuts: white lines that go through the center of the ellipse.
Grey lines mark 45° sectors on a concentric circle.
Through which points should the two other straight cuts go?
You have to traverse the maze to the treasure chest making only right turns.
How many times do you turn right?
How many people of the baby's ancestors were women?
From the available cards shown, we can choose a selection that add up to 33.
What is the smallest possible number of selected cards?
If you randomly break a stick into three pieces, what’s the probability that they can form a triangle?
The numbers from 1 to 2048 are placed clockwise on a circle. We move around the circle clockwise erasing every other number until only one number remains.
If we start by erasing 1, what is the last remaining number on the circle?
Twenty people with excellent shooting records have a friendly meeting in a saloon. Exactly at midnight, each of them makes only one shot and successfully kills the nearest guy.
What is the greatest possible number of criminals that can leave the saloon alive after the shooting?
Jane wants to place several stools in an empty room so that the numbers of stools near each of the four walls are different.
What is the least possible number of stools that she takes?
Look at the list of famous captains.
Find the odd one out.
Look at the list of famous explorers.
Find the odd one out.
Anton lent Boston $100 at 10% weekly interest.
On the same day, Boston lent Colton $100 at 20% weekly interest.
On the same day, Colton lent Anton $100 at 30% weekly interest.
The boy who had money at the end of the first day doubled it in a week, then paid his debt.
The others also paid the debts.
For whom was the operation profitable?
A rooster was born on January First, year 5 BC and died on January First, year 5 AD.
How many years did he live?
Ten girls and several boys attend a dance party.
The girls secretly sorted themselves into alphabetic order by name.
The first girl dances with 1 boy.
The second girl dances with 2 boys.
The third girl dances with 3 boys.
. . .
The tenth girl dances with 10 boys.
Each of the boys dances 5 times with a girl.
How many boys attend the party?
I would like to open a ring so that all rings are separated.
Which ring do I need to open?
Three of the links look like Borromean rings that are used in the coat of arms of the aristocratic Borromeo family in Northern Italy.
A girl is facing a flat (planar) vertical mirror in front of her.
She sees herself entirely.
If she moves two steps back what does she see?
How many bottles can you place on a table so that the distance between any two blue covers is the same?
Find the largest possible number of bottles.
What is the smallest number of straight cuts needed to obtain four pieces of an orange and five peels after eating them?
There are three ducks in front of other ducks, three ducks behind other ducks and three ducks in between other ducks.
What is the minimum number of ducks?
Twelve teenagers, all of different heights, stand in a circle.
Each person who is taller than both his/her neighbors raises their right hand.
Each person who is shorter than both his/her neighbors raises their left hand.
What is the smallest number of raised hands that can be seen?
Once upon a time, a man decided that the time displayed on the village church clock (4:10 p.m) was wrong, although the clock still seemed to be running correctly.
He went to a nearby village, and noted the correct time was 4:30 p.m. before returning.
The clock in his village showed 5:20 p.m. on his arrival.
Which time did he set on the clock?
On average, who have more blood brothers?
You are in a closed room and there are several doors in front of you.
You may open only one door to escape.
Which door do you open?
You met a magician who gave you two big diamonds and said:
"If you tell me a lie I will take back the two diamonds.
If you tell me a truth I will take back only one diamond."
What do tell him to keep the two diamonds?
A granny put on a table three baskets with 4 apples each to equally share between a number of her grandchildren.
How many apples did each grandchild get?
Gerry attached a rope with several cans to his car.
At which speed should he drive the car so that he doesn’t hear the noise of the cans?
Note: Mach Speed is when an object moves faster than the speed of sound. This is 768 mph, 343 m/s, or 1,235 km/h.
Multiply your age by 100, add your age 11 times, and multiply by 91.
What will you get?
Mr. Greedy had 6 apples.
He gave a half to a girl.
How many apples does Mr. Greedy have now?
On what day of the week did the family celebrate the birth of their only male child?
Give the first letter of that day.
In a garden, Alex took as many apples as his son.
Bob took as many apples as his daughter Carole.
All together they took 21 apples.
How many apples did the girl take?
A Math Magician asks a person to secretly choose three numbers. Then he asks the sums of the numbers in pairs. The three sums are 16, 24, and 30. The Magician says the three secret numbers correctly.
What is the largest of the three numbers?
Jane had eight sheep.
All but five fled last week.
All but three were sold this week.
How many sheep are left?
What are ten things you can always count on?
The quantity of oil in each can is different.
Which can contains more oil than the others?
Jane’s granny prepared a large basket of five different fruits for her granddaughter.
In the basket,
20 pieces are not apples,
22 pieces are not bananas,
24 pieces are not clementines,
26 pieces are not dates,
28 pieces are not egg-fruits.
How many apples were there in the basket?
Which is true?
A boy from the island of Great Britain travels in North America.
A local person asks him:
"There are so many European languages.
Why do people on your island speak an American language - English, not a European language?"
What would be a polite answer to the question?
There are 16 rooms in a square castle, all the rooms being connected as shown.
Our prince is in the yellow corner room.
He wants to meet as many girls as possible before leaving the castle via the green exit.
He refuses to meet any particular girl more than once.
What is the maximum number of girls our prince is able to meet?
Miss Smith gives Mary a piece of paper and
asks "How many stars are there?"
Mary says "Three".
Miss Smith says "Correct!"
Miss Smith gives John the same piece of paper and
ask the same question.
John says "Four".
Miss Smith again says "Correct!"
How many stars are there on the piece of paper?
A web designer adds several stars to the picture of the Moon.
How many stars are placed incorrectly?
Circulating US coins - penny, nickel, dime, quarter - are the coins that the United States Mint produces for everyday transactions.
Penny = 1 cent.
Nickel = 5 cents.
Dime = 10 cents.
Quarter = 25 cents.
What is the least number of coins you need to pay, in exact change, any amount from 1 cent to one dollar (100 cents)?
Remove two from "FIVE" to make four.
Which two do you remove?
Gerry and Jane play a game: each takes off one or two neighbouring white petals from the flower. Gerry starts first. The winner takes off the last petal.
Is there a winning strategy? If yes, who wins?
Move just one matchstick to make the largest possible number.
From which number do you choose the matchstick?
John and Mary share a delicious triangular cake, the sides of the triangle being equal. John chooses a point on the cake, and Mary makes a straight cut through that point, taking the larger piece. Both teenagers want to get as much as possible.
What part of the cake might John obtain if his girl-friend is very strong in geometry?
A mouse (green point) at a crossroads of a labyrinth senses where two identical pieces of cheese (red points) are.
The shortest distances within the labyrinth from the mouse to the two pieces of cheese are the same, in this case two units.
How many crossroads in total are there in the labyrinth, from which the shortest distances to the two pieces of cheese are the same?
To be clear, from any suitable crossroads, the distances to both pieces of cheese have to be equal to each other, but not necessarily two units long.
Girls and boys, totalling 33, hold hands in a circle.
Twenty of them hold hands with at least one boy.
Twenty seven of them hold hands with at least one girl.
How many girls are there?
There is an error in the sign on a street during an infection.
What kind of error is it?
The Eiffel Tower is a wrought-iron lattice tower in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower. The main structural work was completed in 1889. The tower is 330 metres (1,083 ft) tall, about the same height as an 81-storey building, and the tallest structure in Paris.
At which of the four dates was the tower the tallest?
Wording Brain Teaser
Make one word from all the following jumbled letters:
E D N O O R W
Which letter is the last?
Wording Brain Teaser
Which word with another 4-letter word, when combined, holds the most letters?
Alex, Bill, Carl, and David play a game. One by one (in the alphabetic order) they break the Swiss chocolate bar along the lines until all the pieces are 1x1 bars. Nobody cannot break two or more pieces at once.
The last person who is able to separate a bar is the winner.
Do you know a winning strategy? Who is the winner?
Jane encoded a message for Gerry.
Guess what it says.
Gerry's salary is 60% of his boss's salary.
By what percentage should his boss's salary decrease and Gerry's salary increase to become equal?
Three young brothers weigh together 333 kilograms (kg).
Albert weighs 7 kg more than Boris, who is 7 kg heavier than Caesar.
What is the weight of Albert?
When you press a button the face changes, and so do the faces of the neighbouring buttons.
Button faces come in two basic types: smiley and frowny. A smiley face changes to a frowny face on being pushed. Likewise, a frowny face turns into a smiley face.
What is the minimum number of button presses needed so that only smiling faces can be seen?
On an island, all 77 inhabitants are either knights, who always tell the truth, or knaves, who always lie.
They all meet on a beach on January 1st, look around, then cry out at 12:00 noon
"All of you are knaves!"
How many knights are there on the island?
A shoe lace is lying on a table, with as many crossing points as shown in the image.
The lace is equally likely to pass over itself or under itself when we move from one end to another.
What is the probability that the shoe lace is knotted after its ends are pulled?
Avany and Bavany are twin sisters who walk with the same walking speed, and run with the same running speed.
They take a trip to their Granny's cottage.
Avany walks for half the distance, and runs for half the distance.
Bavany walks for half the time, and runs for half the time.
Who is the first to arrive at Granny's cottage?
Which number is decreased by 12 if you turn a piece of paper on which it is written upside down?
I am heavy forwards, but backwards I am not.
What am I?
A cowboy gallops into a town on Friday, participates in a rodeo, stays for two days, and leaves the town on Friday.
How many days does he stay in the town?
The photograph courtesy of Roland Sauter
Why can't a man living in the United Kingdom be buried in the French Republic?
A Swiss ten-centime coin from 1879 holds the Guinness World Record for the oldest original currency in circulation.
Guess who is on the front of the coin.
Brain Teaser
If three is a company and four is a crowd, what are four and three?
10 + 10 and 15 + 7 are the same thing because 10 + 10 is twenty and 15 + 7 is twenty too.
A 3 kg cat is standing still on all four legs with its weight evenly distributed between its legs. For no clearly defined reason it lifts one paw off the ground and stands still on just three legs, again with a uniform distribution of weight.
What was the change of weight passing through one of the paws still in contact with the ground?
The standard roll of toilet paper is about 302 feet long.
If Santa Claus walks at a speed of 5 feet per second, how much time does it take for him to walk the distance of the roll length?
There are 4 lines of smiley faces. Some of the smiley faces are either partially or fully covered by a splat of white paint.
How many more smiley faces are splattered than ones that are untouched by the paint?
The first customer bought half of all the eggs and a half of an egg.
The second customer bought half of all the eggs that were left, and a half of an egg.
The third customer bought half of all the eggs that were left, and a half of an egg.
The fourth customer bought half of all the eggs that were left, and a half of an egg.
No eggs were left in the shop.
What is the least possible number of eggs that were in the shop at the beginning?
A man said about his age:
"You obtain my age if you subtract 5 times my age five years ago from five times my age in five years."
How old is he?
Every day, invested money doubles in the Mad Money Bank. A client has to pay $120 fees at the end of every day.
John has opened a new account in the bank. In three days the bank informs him that his balance is zero.
How much money did he put into the account?
There are 13 pirates on a ship.
One pirate always tells the truth.
At least one pirate in any pair lies.
How many pirates are there on the ship who tell truth?
The Ninth Symphony of Beethoven is twice as long as the First Symphony.
If 12 musicians play the First Symphony in 30 minutes, how much time does it take for 6 musicians to play the Ninth Symphony of Beethoven?
A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as racecar.
Punctuation, capitalization, and spaces are usually ignored.
Which phrase is not a palindrome?
There were about 200 countries (196 countries in 2010) in the world.
The country names start with almost all letters of the English alphabet, except
A drinks dispenser has three labelled buttons: JUICE, SODA, and LUCKY. If you press LUCKY you are supposed to get either juice or soda with equal probability. Each button is wired to exactly one of these functions, and all of the functions are connected. Due to a miscommunication, the LUCKY button has definitely been wired up to some other function. One button is definitely wired up correctly.
Assuming that you are clever, but unlucky, how many button presses are required to establish exactly which button does which function?
Sailors have used a unique bell code to tell time at sea for hundreds of years.
The watch officer struck the ship’s bell every half hour to apprise the crew of the time. A single bell denoted the end of the first half hour, and one bell was added each half-hour. Eight bells therefore signaled the end of each four-hour watch.
First Watch 8:00 p.m. to 12:00 a.m.
Mid-Watch (also Black Watch) 12:00 a.m. to 4:00 a.m.
Morning Watch 4:00 a.m. to 8:00 a.m.
Forenoon Watch 8:00 a.m. to 12:00 p.m.
Afternoon Watch 12:00 p.m. to 4:00 p.m.
Evening Watch 4:00 p.m. to 8:00 p.m.
For example, one bell at 00:30, two bells at 01:00, . . . eight bells at 04:00.
The cycle starts again with one bell.
What is the total number of times the bell is struck in 24 hours?
My first is A, as you can C,
then F and J -- are on my way,
but O is just a step away
... "from what?", I thought I heard you say.
If the probability of meeting a wolf in the forest in 3 hours is about 0.1, what is the probability of meeting a wolf in the forest in 1 hour?
When is it safe to jump out of an airplane without a parachute?
Mario has 44 lives remaining and 9 levels to complete. He loses one life on the first level.
He loses one life more than on the previous level on each level he completes.
How many lives will he have left after completing the 9 levels?
A thumb war tournament had four players. Each player played every other player only once, with no ties.
Anna won 2 games, Bill won 1 game, and Cindy won 1 game.
Who scored better?
In a certain everyday environment, people say that 1530 plus something and 1700 minus something are the same thing.
What is the "something" if it is not 85?
Benny Bunny has three types of carrots of lengths 10cm, 15cm and 17cm.
What is the least number of carrots he can use to mark out a distance of 33 cm?
About 37 million people live in the urban area of Tokyo, Japan.
Estimate how many boys there celebrate their birthday on April, 1st.
If Gerry weighs 72kg, Jane ¾ of his weight, and a pumpkin weighs 12kg, what is the minimum number of pumpkins that outweighs Gerry and Jane?
Sami's truck loses 1/16 of the straw packs every time it bumps into another car.
If Sami started today with 256 packs and has bumped twice into other cars, how many straw packs are lost?
Atlantic tropical storms are named through a strict procedure by an international committee of the World Meteorological Organization.
How many names are there in the table?
The Arecibo message was a short radio message sent into space to celebrate the remodeling of the Arecibo radio telescope in Puerto Rico in 1974. It will take 25,000 years for the message to reach the stars, and at least another 25,000 years to get any reply.
The first part of the message (the picture at the right) shows the numbers one (1) to ten (10).
What fraction of the messages is white squares?
There are 7 employees in a company. A new manager arrives and fires every second employee.
In one year the manager moves to a floor polisher position and a new manager arrives. He fires every second employee.
In one year the manager moves to a floor polisher position and a new manager arrives. He fires every second employee.
If the process continues every year, how many people are there in the company now?
A king travels at a speed of 8 km/h from his castle to a battle. Each four hours he sends a messenger with a speed twice as fast as the king back to the castle.
How often does the queen in the castle receive the messages?
Alice is a well-educated, law-abiding girl. She goes to her school.
Can you guess the country where she lives?
I have hares and carrots.
If I give one carrot to each hare, I will have one carrot too many.
If I try to give two carrots to each hare, I will be one carrot short.
How many hares do I have?
The Happy Town Council decides not to use unhappy numbers (4 and 13) and their multiples.
If the last house number in Happy End Street is 110, how many houses are there in the street?
A professor of mathematics Cal Culus is 68 years old.
He declares: two-thirds of the time before my marriage is equal to three-quarters of the time after it.
At what age was he married?
A question at a job interview.
A bathtub is ¾ full of water.
You have a teaspoon, a teacup, and a bucket.
What would you use to empty the bathtub?
A helicopter starts from an Australian military base and flies 200 km south, then 200 km east, then 200 km north, and then 200 km west.
Where is it now compared to the departure point?
Do coconuts sink or float?
The average American male is 5 ft 9.3 in (1.76 m).
The average player in the National Basketball Association (NBA) is listed at 6 ft 7 in (2.01 m).
Estimate of the height of the hoop above the ground.
Six classmates each have a different piece of shocking news which they will communicate by phone. Each phone call between exactly two classmates takes 1 minute, at the end of which they both know the same amount of news.
What is the shortest time required to communicate all the news to all the classmates?
A hunter tells a fellow that he saw a lion in a desert near their village.
The guy tells his wife that 2 lions were seen in the desert nearby.
The woman tells a neighbor that 6 lions were seen in the desert.
The neighbor tells another woman that 12 lions were seen in the desert.
A man always doubles the number of lions, while a woman triples the number.
Somebody tells the patriarch of the village that 144 lions were seen in the desert nearby.
How many people spread the news?
A barber wants to write the word COOL on a board behind the client’s seat in such a way that a client looking in the mirror reads the word correctly.
Which of the following should the barber write on the board?
What does the secret message tell you?
251521 1185 191311820
The first four Volumes of the Delicious Food Encyclopedia are stacked vertically side by side on a shelf. There 400 pages in each Volume.
A well-educated worm ate paper in a hole from the first page of the First Volume to the last page of the Fourth Volume.
How many pages did she taste?
There are 3 hockey pucks on ice.
A player shoots one of them between the two others. Then he repeats the shots always choosing another puck. He shoots all three pucks.
After how many shots can he get back to the original positions of the three pucks?
Father promised John 1 cent for 1 solved problem, 2 cents for 2 solved problems, 4 cents for 3 solved problems, 8 cents for 4 solved problems, . . .
John finished the weekend with an extra $20 and several cents in his pocket.
How many problems did he solve?
A clock chimes once on the quarter hours, and chimes the hours according to the hour.
For example, at 1 pm there is 1 chime, and at both noon and midnight there are 12 chimes.
There are in 220 chimes in 23 hours and 59 minutes.
When did the time interval start?
Weighing a hyperactive boy was a big family problem.
His father held the boy and stood on the scales while mother read off 88 kg.
Then mother held the boy while father read off 66 kg.
Then father held beloved mother while the boy read off 144 kg.
What was the combined weight of the family?
The wife of a rich man was pregnant.
Her sick husband demands that after his death his 42 million fortune should be split according to the following rules:
a new born girl receives twice as much as the mother OR
the mother receives twice as much as a new born son.
The rich man successfully died, but his wife gave birth to twins: a boy and a girl.
How many times more money does the girl receive than her brother?
Swiss public schools usually use a 6-point grading scale, where 6 represents the highest grade and 1 the lowest possible one.
6 (excellent) is the best possible grade. (100%)
5.5 (very good) (90%)
5 (good)(80%)
4.5 (satisfactory)(70%)
4 (sufficient) (60%)
3.5 (insufficient) (below 50%)
3 (poor) (40%)
2.5 (very poor) (30%)
2 (very poor) (20%)
1.5 (very poor) (10%)
1 (very poor) (0%)
If Hans got 3 fives, 2 fours and 1 one, what is his average score?
A helicopter starts from a Canadian military base and flies 200 km south, then 200 km east, then 200 km north, and then 200 km west.
Where is it now compared to the departure point?
What is the correct name for water containing quite a lot of dissolved calcium carbonate?
There is only one entrance into an apartment building via the ground floor.
One person lives on the first floor, two people live on the second floor, three on the third floor, four on the fourth floor, five on the fifth floor, six on the sixth floor, and one lives on the seventh floor.
Which button is more frequently used in the lift (elevator) of the building?
The train moves to the east.
Which point of the wheels moves in the opposite direction?
I am nothing, not something.
You can see me only where I am not.
I am made from two things, yet I am still nothing.
What am I?
The ancient Egyptians made a right-angled triangle using a rope with knots. The knots were at equal distances apart.
How many knots were there on the rope?
A runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°). There are two numbers at different ends of a runway. There is 13 at an end of a runway.
What is the number at the other end?
I have a 'Christmas tree' that is green from both sides.
I would like to cut it into separate pieces and compose a rectangle.
What is the minimum possible number of straight cuts I should make?
In number theory, a polite number is a positive integer that can be written as the sum of two or more consecutive positive integers.
Can you define the rule of being 'impolite numbers'?
Data Analysis:
Which group represents the best liars?
by Leslie Green
A banker has a brother, who is a plumber. The plumber is married to a nurse and they have two children - two boys.
Which statement can be true?
How many mistakes are there on the blackboard?
Tricky Equation Puzzle: the equation below is wrong:
62 - 63 = 1
Which numeral has to be moved to make the equation correct?
What is the minimum number of cuts Gerry has to make in a 12 x 12 carpet so that it fits a room with dimensions 16 x 9?
Atlantic tropical storms are named through a strict procedure by an international committee of the World Meteorological Organization.
Based on the given table, guess how the tenth hurricane in 2023 might be named.
Sometimes I hold bad people.
Sometimes I am the smallest unit of a living organism.
Other times I make your torch work.
What am I?
Big Ben is the nickname for the Great Bell of the clock at the north end of the Palace of Westminster in London, United Kingdom. Big Ben is the hour bell. For example, at four o'clock, four chimes ring from the great bell in 12 seconds.
How long does it takes to ring ten o'clock?
You can listen to Big Ben by clicking on the link.
Six points are randomly chosen at the edge of a pizza.
Three straight cuts are made by passing through two of the points, never the same.
What is the largest possible number of pieces that can be made?
The term "per cent" is derived from the Latin per centum, meaning "by the hundred".
According to the Royal Statistical Society, 10% of the UK adult population does not understand percentages.
Which example confirms this?
Jim asks: "If John's son is my son's father, what relationship am I to John?"
When counting, what number is greater?
This is a shop price tag written in French.
The tag says that BN Mini duo cereals are on sale for 3.95 instead of 3.15.
Is the rebate really 20% off?
The terms anno Domini (AD) and before Christ (BC) are used to label the number of years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin and it is taken from the original phrase "anno Domini nostri Jesu Christi", which translates to "in the year of our Lord Jesus Christ".
An archaeologist finds three coins with different notations.
Which coin is fake?
In a democratic country, 75% of the electorate vote in a particular election. The candidate 'Rob the Slob' wins the leader's election with 60% of the vote.
What proportion of the population definitely wanted Rob the Slob as their leader?
by Leslie Green
FOUR + FIVE = NINE
Each letter represents a unique digit in the cryptarithm.
What is the smallest possible value for NINE?
The picture shows a subway map.
A team of inspectors verifies passengers' tickets at a station on a line, or all lines through it if there are many lines.
Then they randomly choose the next neighboring station and move there to make their inspection.
At what station does Gerry have more chance of being inspected?
In what Olympic competition does the winner cross the finishing line facing backwards?
A girl is facing a flat (planar) mirror in front of her.
What is the minimum possible height of the mirror in order for her to see herself entirely in the mirror?
Leslie Green asks:
Why can kid's questions seem so boring and unrelated to real life?
Greek Mathematician Eratosthenes measured the circumference of the Earth in 240 B.C.
He put two vertical sticks of the same length in the ground and measured their shadows in Alexandria and Syene that were 800km apart at the same day and time.
The shadow was absent in Alexandria. The shadow corresponded to angle of 7.2° in Syene.
Based on the information can you calculate the circumference of the Earth?
A word can be attached to the beginning of GUARD, LAND, LINE, and WARD to give a longer word in each case.
How many letters does the word have?
In Healthy Drink city, at the last Mayor’s election 100 votes were polled.
The Apple Juice Party candidate was elected by a majority of 3 over the Spring Water Party candidate, by 4 over the Green Tea Party candidate, and by 9 over the Cow's Milk Party candidate.
How many votes were polled for the winner?
Which proverb has a different meaning than the other three?
A newly married couple started walking and finished at the same point of Paris.
Was it possible to walk and cross over each of the bridges only once in 1657?
If one elf can make two elves after an hour of work, how many elves are there after 5 hours?
Logic Puzzle
Two fathers, two sons, and two doctors had a healthy breakfast.
Each person ate an apple.
What is the least possible number of apples that have been eaten?
A claustrophobic gentleman chooses his place in the train that will enter a tunnel just after the station.
Where is the best place for him?
How many phrases below are spelled the same written forward as backward?
Samples of Palindromes
Madam, I’m Adam
Top of spot
No lemon, no melon
A counting-out game
People are standing in a circle.
Counting begins at a person in the circle and proceeds around clockwise. The player who is selected at the conclusion of the rhyme is out.
The count starts with the next person.
Four children stand in a circle in the following order: Alex, Betty, Craig, and Diana.
If the count-out game starts from Alex, who will win the game?
They use the most common English rhyme:
Tinker, Tailor,
Soldier, Sailor,
Rich Man, Poor Man,
Beggar Man, Thief.
Which is certainly a fake coin?
Leslie Green asks:
It was announced on the UK news that birds were flying backwards in a certain location at a certain time.
Suggest the most plausible explanation for this report.
How many letters are there in the word which becomes shorter after adding two letters at the end?
If certain words in this question are spelt wrong, how many of the eighteen words are spelt wrong?
You meet a boy from a region of two cities: Truth City and Lies City. Truth City dwellers always tell the truth, and Lies City dwellers always lie.
If you want to know the direction to Truth City at a fork of two roads what question will make him direct you correctly?
Logic Puzzle
There are only X types of people:
those who understand binary and those who don't.
What number can replace X?
Logic Puzzle.
A European country has the highest ratio of men to women among its population in the world.
What is the first letter of the country name?
Leslie Green asks:
In ancient texts, when writing materials were expensive, it was usual to write without punctuation and without spaces between the words.
In this well known English language proverb, how much space has been saved, assuming that every character and space takes the same amount of room (a fixed-pitch font)?
Logic Puzzle.
Many years ago a king of a North European country decided to establish which is more dangerous for health: tea or coffee.
He ordered that one prisoner should only be given coffee, and that another prisoner should only be given tea.
What do you think? Who died first?
Leslie Green asks
"Mary has a cat, and a rat, and a hat, and a mat.
If the cat is on the mat, and rat is in the hat, but the hat is on the mat, where is the rat?"
In a competition "The Best Smile of the Year", twenty participants successfully failed to pass to the final stage of the competition.
This is 40% of the total number of participants.
Of course, handsome Johnny passed to the final.
How many participants passed to the final stage of the competition?
Kevin cleans rooms in a student hostel; he earns twice as much for cleaning a large room as he does for cleaning a small room. Yesterday he cleaned five large rooms and three small rooms. If, instead, he had cleaned three large rooms and five small rooms, he would have earned $20 less.
How much did he earn yesterday?
Number SEVEN is mystic and frequently used in human culture.
What is the most reasonable cause of that fact?
Leslie Green asks:
An American salesman flies over to London (UK) and for reasons best known to himself carelessly steps out of a first floor window. He breaks his leg.
Why?
Pop Quiz Paradox
A teacher announces to his class that there will be a quiz one day during the next week. The teacher gives the definition that they would not know when they came in to class that the quiz was going to be given that day.
The brightest student says that the quiz cannot be on Friday because they will know the day on Friday. With the same technique, she eliminates Thursday, then Wednesday, Tuesday and Monday.
"You cannot possibly give us a pop quiz next week," she says.
When does the teacher give the pop quiz?
I know the paradox from Charles Carter Wald. Probably, Martin Gardner described the quiz for the first time in The Colossal Book of Mathematics.
The ball's design stitches together hexagons with pentagons. The ball made its World Cup debut as Adidas' Telstar in 1970 in Mexico. The ball's pattern of white hexagons with black pentagons made it easily visible on television.
If there are 12 pentagons, how many hexagons are there?
What is the sum of the interior angles of the Bermuda triangle?
These guys gallop at speed of 25 km/h and walk on foot 10 times slower.
How much time does it take for them to ride to a stable, which is 5 km away and come back on foot?
I take off from Brussels, Belgium and fly 777 miles due south. Then, I turn the plane and fly 777 miles due west. I turn again and fly 777 miles due north, and finally turn and fly 777 miles due east.
Which country do I land in?
A teacher explains to his students about taxes by eating 30% of their ice cream.
If each of 24 students has a cone of ice cream, estimate the amount of ice cream the teacher ate?
A white hen lays an egg every third day.
A black hen lays an egg every second day.
How many eggs in total do a white hen and a black hen lay in November?
Brainteaser: A word becomes shorter when you add two letters to it.
How many letter are there in the word?
If Edgar cleans his teeth twice per week and changes the toothbrush every time he uses it, how many brushes does he need every year?
There are two gods named Mendax and Fidelis, one on your left, the other on your right, but you do not know which is which. Fidelis always answers correctly. Mendax only answers one question in 7 correctly in a repeating cycle. You do not know which part of the cycle Mendax is currently on.
You must determine which god is which using the minimum number of YES/NO questions. How many questions do you need to be certain?
To clarify the matter, if Mendax is answering incorrectly, your entire question is evaluated correctly and then the answer is reversed. A single question to both gods counts as two questions.
Author : Leslie Green
Inspired by G. Boolos. 'The hardest logic puzzle ever', The Harvard Review of Philosophy (6), 1996.
The King of a far away land needs to adjust the temperature of the shower all by himself. The inconsiderate servant who normally performs this duty has broken his leg and is therefore unavailable. (The King has failed to realise that kicking the servant caused the servant to trip, breaking his leg because of the fall!)
The King requires a flow rate of 4 liters per minute of 40°C water to be derived from two calibrated hot and cold water taps. The cold water is at 10°C and the hot water is at 50°C. The mixing unit does not change the calibration of the taps or allow heat to be lost from the water.
What settings are required on the taps?
The problem was suggested by Leslie Green
Derek dragon became a vegetarian two years ago. Derek likes to eat 3 baskets full of apples and 5 baskets full of berries for his birthday feast. But this year he can’t find many berries so he settles for 4 baskets of apples and only 1 basket of berries instead. Surprisingly, he feels equally satisfied. His mind drifts back to the old times when humans in metal suits used to clank into his cave. They made a nice crunchy breakfast treat!
How many baskets of berries will satisfy this dragon for his next birthday feast?
Sammy the sea lion has spotted a gorgeous Lady sea lion before anyone else. She is in the sea and he is on the beach. The picture shows the distances in hundreds meters. He needs to get to her as soon as possible to avoid any potential rivals getting to her first.
He can travel three times faster in the sea compared to on the sandy beach over the distances involved.
Which route should he use?
The problem was suggested by Leslie Green
If it rains at midnight in London, what are the chances that it will be sunny in 72 hours?
Buy 2 for the price of 3 and get 50% off!
What is the final discount you get?
'Buy, buy, says the sign in the shop window; Why, why, says the junk in the yard.' - Paul McCartney
There are two gods named Orbis and Fidelis, one on your left, the other on your right, but you do not know which is which. Fidelis always answers correctly. Orbis only answers alternate questions correctly; you do not know if his last answer was correct.
You must determine which god is which using the minimum number of YES/NO questions. How many questions do you need to be certain?
To clarify the matter, if Orbis is answering incorrectly your entire question is evaluated correctly and then the answer is reversed. A single question to both gods counts as two questions.
Author : Leslie Green
Inspired by G. Boolos. 'The hardest logic puzzle ever', The Harvard Review of Philosophy (6), 1996.
Coin landing on its edge
I flip a fair Swiss franc* and it falls in mousse**.
What is the probability that the coin stays on its edge after the mousse melts?
*One Swiss franc is about 1 USD; diameter 23.20mm , thickness 1.55mm, weight 4.4g.
During a coin toss, the coin is thrown into the air such that it rotates edge-over-edge several times.
**A mousse (French 'foam') is a prepared food that incorporates air bubbles to give it a light and airy texture.
A short word can be written forward, backward or upside down while remaining the same word.
What is the first letter of the word?
When Pinocchio lies, his nose gets twice as long.
When he tells the truth, his nose gets 1 cm shorter.
His nose was 1 cm long in the morning, and it is 100 cm long in the evening.
What is the least possible number of times he opened his mouth today?
A shopkeeper of a Dairy stands six feet tall and wears size 13 sneakers.
What does he weigh?
If you were to spell out the numbers, how far would you have to go before encountering the letter 'a'?
According to research, an average waist circumference of American men is greater than 40 inches (1 meter).
A $1 bill measures 156 mm long and weighs approximately 1 gram.
How many $1 bills are needed to cover the waist?
Gerry gave half of his money to Jane.
Next day, she gave half of all her wealth to Gerry.
After the last exchange they each have exactly as much as they originally started with.
Who is richer?
Around 95.83% of the students in a class that James is in have different numbers of hairs than he has.
How many students are there in his class?
According to Wikipedia Mrs. Vassilyeva holds the record for most children: she gave birth to a total of 69 children: sixteen pairs of twins, seven sets of triplets and four sets of quadruplets between 1725 and 1765, in a total of 27 births.
How many single children were born?
At the end of each week, Gerry forgot 50% of what he knew the week before.
At the end of which week Gerry knew less than 50% of all he studied?
Veryfast Airlines loses 20% of the luggage.
Gerry puts his three favorite toys in three different bags.
What is the probability that he no longer has any toys after flying with Veryfast Airlines?
If Gerry gives Jane one apple, they will have the same number of apples.
If Jane gives Gerry one apple, he will have twice as many apples as she has.
How many apples do they have?
Gerry is a gentleman and so always gives Jane apples.
Jane picks a random integer between 1 and 5 (inclusive) and Gerry does the same.
They then compared their numbers.
What is the probability that Jane's number is greater than Gerry's number?
What is the maximum number of sections into which a pancake may be divided by four straight cuts through it?
(NOTE: The pieces cannot be re-arranged between cuts.)
Gerry's circular garden is 1200 m in diameter and has no fence.
How far can a wolf run into the garden?
Which is correct?
The knights gallop 100 m in 10 seconds.
There are 1000 m in 1 km.
Would the knights get a fine if the speed limit is 40 km per hour?
"This is a capital letter of the alphabet that's been folded just once.
Which letter is it if I unfold it? "
The puzzle was created by puzzlemaster Scott Kim
How long do One Thousand and One Nights last?
A Persian king, Shahryar, begins to marry a succession of girls only to execute each one the next morning. Scheherazade, the vizier's daughter, decides to be a bride. On the night of their marriage, Scheherazade begins to tell the king a tale, but does not end it. The king, curious about how the story ends, is thus forced to postpone her execution in order to hear the conclusion. The next night, as soon as she finishes the tale, she begins (and only begins) a new one, and the king, eager to hear the conclusion, postpones her execution once again. So it goes on for 1,001 nights. Source : Wikipedia
There are 5 children in a boat.
Four of them do one of the activities below.
What is the fifth kid doing?
A pirate boat is floating on a lake.
The pirates throw a heavy chest with gold coins overboard.
What happens with the water in the lake with respect to the shore?
How many uninteresting numbers exist?
The question is based on the interesting number paradox, which is a semi-humorous paradox, which arises from the attempt to classify natural numbers as "interesting" or "dull."
Five students Anna, Bill, Craig, Daniel, and Eugene commute by bus. Every morning each student independently and randomly boards one of the four available school buses.
What is the average number of students in the bus that Anna chooses?
A father has left 47 donkeys for you to distribute to his three sons;
1/2 (23.5) should go to his eldest son,
1/3 (15.667) to the middle one, and
1/8 (5.875) to the youngest.
You arrive with your own donkeys.
You can add or take some donkeys from the herd.
How do you divide them so that all sons are happy with your decision?
How many donkeys does the eldest son get?
Inspired by Malba Tahan “The man who counted.”
After a test of a code, John detected 2 errors and Mary discovered 3 errors in the same code.
There is one error in common.
Estimate the number of errors that are still undetected.
The size of a swimming pool is 25 x 12.5 meters.
How many people must jump into the pool so that the water rises by 1 meter?
How high is a $50,000 stack of $1 bills, given that the thickness of 100 bills is about 1 centimeter (0.033 feet)?
Gerry sent three letters to three girlfriends.
The postman put the letters into three different boxes without looking at the name of the recipient.
What is the probability that all girls received their letters?
A swimming pool is 12.5 x 8 x 3 meters.
The average volume of a human body is 0.066 cubic meters.
How much does the volume change if 10 swimmers jump into the pool?
Andrew is expecting two important 10-minute phone calls today at a randomly selected time from 2:00 p.m. to 3:00 p.m.
What is the probability that he will not be able to answer the second call because he is talking with the first caller?
I place 11 chairs along the walls in an empty rectangular room.
The number of chairs along each wall is the same.
A chair cannot be stacked one on top of another.
Find the number.
Mount Everest is the Earth's highest mountain with a peak at 8,848 meters (29,029 ft) above sea level.
Indian mathematician Radhanath Sikdar was the first to identify Everest as the world's highest peak in 1852. Edmund Hillary and Tenzing Norgay reached the summit on 29 May 1953.
What was the highest mountain in the world before Mount Everest was discovered?
Is it legal for a man in Montana to dance with his widow's sister at her marriage ceremony?
A four-letter word can be written forward, backward or upside down while remaining the same word.
What is the first letter of the word?
After a three-hour drive, I stopped my car in front of a wall with three doors: a silver door on the left, a gold door in the middle, and an iron door on the right. Which door would I open first?
"Letter frequency. Accurate average letter frequencies can only be gleaned by analyzing a large amount of representative text." (source: Wikipedia)
What is the most common letter in the English alphabet?
Logic riddle:
In a house, there are three switches on the ground floor and a light bulb in the cellar. I cannot see the light from the ground floor.
What is the minimum number of trips to the cellar I need to make to identify which switch corresponds to the light bulb?
We assume that the bulb in the cellar works, that there is power to the house, and that one of these three switches will switch on the cellar light.
If you are a redhead you have more than the average amount of hair.
This statement is . . .
If 2 salesmen can sell three luxury cars in 4 days, how many luxury cars can five salesmen sell to six clients in 7 days?
Logic question.
What is the easiest way to make the following equation correct?
Bob shaves himself for 3 minutes every day, including the weekends.
If he starts shaving at the age of 20 and lives 70 years, what is the total amount of time spent shaving?
An average baby is about 20 inches (51 cm) long and weighs approximately 6 to 9 pounds (2700 to 4000 grams).
How many times heavier than a baby is an adult?
Logic puzzle: a secret door.
A man approached the door of a secret laboratory and the door robot said "SIX." The man replied, "THREE" and was let in.
Another day, the robot said, "TWELVE."
The man replied, "SIX" and was let in.
Today, the robot said, "TWENTY."
What should the man say?
I participate in a street-legal car race (on a race track).
One second before the finish I am the first who overtakes the last.
In what position do I finish?
A hammer and a nail cost $21.
If the hammer cost $20 more than the nail, how many times is the hammer more expensive than the nail?
How many apples can I place, such that the distance from every apple to every other apple is a single fixed value?
Given that 80% of IT projects fail, and that 20% of IT managers are female, what percentage of IT projects are both successful and have male managers?
Ninety-nine percent of John's nuts and 99% of a nut cost as much as all his nuts. How many nuts does he have?
Logic puzzle:
What happens once in a minute, twice in a week, and once in a year?
What is the maximum amount of Xs that you can you place on a Tic-tac-toe board without making three-in-a-row in any direction?
It takes exactly 1 hour to burn a rope when I light one of its ends.
The rate of burning is completely random, but the final result is always 1 hour.
How many different periods of time can I measure with 2 such ropes?
A donkey must transport 900 carrots to the market, which is 300 miles away.
The donkey carries a maximum of 300 carrots, and eats 1 carrot every mile.
What is the largest number of carrots that can be delivered at the market?
I took several pieces of fruit from the bowls.
All of them are cherries except two, all of them are apricots except two, and all of them are red currants except two.
How many pieces of fruit did I take?
Logic riddle
This occurs once in every second, once in every hour, and twice in every afternoon.
How often does it occur in every month?
Logic riddle
In a house, there are three switches on the ground floor for three light bulbs in the cellar. I cannot see the lights from the ground floor.
What is the minimum number of trips to the cellar I need to make to identify which switch corresponds to which light bulb?
Logic puzzle: a secret door.
A man approached the door of a secret laboratory and the door robot said "SIX." The man replied, "THREE" and was let in.
Another day, the robot said, "TWELVE."
The man replied, "SIX" and was let in.
Today, the robot said, "FOURTEEN."
What should the man say?
If a hen and a half lay one half of an egg in two days and a half, how many eggs does a hen lay in a month?
There is a legend that a stork brings babies to a village.
All parents continue to have children until they have a boy.
If they have a girl, then they try to have another child.
They stop if they have a boy.
The probability of giving birth to a boy is 50%.
What is the proportion of boys to girls in the vilage?
The photograph courtesy of Roland Sauter
Guesstimation.
How many tennis balls can fit in a school bus?
The average hourly wages of men and women in company A are $21 and $16, respectively.
The average hourly wages of men and women in company B are $20 and $15, respectively.
Twenty percent of company A employees are men.
Forty percent of company B employees are men.
Which company pays a higher average wage to their employees?
Anna (A), Bill (B), Cindy (C), and Daniel (D) work on a project.
(1) Together, A, B, and C can complete it in 10 days.
(2) Together, B, C, and D can complete it in 11 days.
(3) Together, C, D, and A can complete it in 12 days.
(4) Together, D, A, and B can complete it in 13 days.
Who is the best performer?
Large individual letters are differently priced.
The letters in the word SPRING cost $19.
The letters in the word SUMMER cost $20.
The letters in the word AUTUMN cost $21.
The letters in the word WINTER cost $20.
How much would the letters in the word SEASONS cost?
There is insufficient information to solve this problem.
Use the simplest assumption which exactly matches one of the answers given below.
Guesstimation.
Anna has 100,000 strands of hair with an average length of 40 cm or 1.31 ft.
How long is her hair?
Remember 1 km = 1000 meters = 100,000 cm = 0.62 miles
Three ducks and four ducklings weigh 3.4kg.
Four ducks and three ducklings weigh 4.3kg.
If all ducks weigh the same and all ducklings weigh the same, what is the weight of a duckling?
Bryan went for a haircut yesterday.
He has 120000 strands of hair and it took 12 minutes to cut all his hairs.
His barber charges $180 per hour.
How much does it cost to cut 1 strand of hair?
A photographer will pay me $3600 per hour of taking a picture of my smile.
How much money will I receive for 1 second of the hard work?
An amoeba is a shapeless unicellular organism.
An amoeba propagates by simple division into two amoebas; each split takes 3 minutes to complete.
An hour ago, I put one amoeba in an empty jam jar.
Now, the jar is full of amoebas.
When was the jar half full?
What would this picture look like in a rearview mirror?
Several students want to rent a car for the next weekend.
If each contributes $12, they lack $4.
If each contributes $14, they have an extra $4.
How many students are there?
A man is eating a pizza.
During the first day he eats a half of the pizza.
On the second day he eats 1/3 of the remaining part of the pizza.
The third day he eats 1/4 of what is left, and the fourth day he eats 1/5 of what still remains.
He then stops because the last piece was not fresh.
What fraction of the original pizza is still available?
Henry has 100 roses.
He gives them to his dancing partners in such a way that each girl gets at least one flower and no two girls get the same number of flowers.
What is the largest number of girls with whom he could dance?
I sold two cars and received sixty thousand dollars for each car.
I received 50% profit on one of the transactions and lost 40% on the other.
What is my net profit on the two transactions?
I completely covered a one square meter area with $100 bills without any overlap or gaps.
What is the least amount of money that I spent if the bill size is 157 x 66 mm and its area is 0.01036 m2?
On September 4, 1781, the full name of Los Angeles was
El Pueblo de Nuestra Señora la Reina de Los Ángeles del Río de Porciúncula.
How many times shorter than the full name is the abbreviated name?
I want to move just one matchstick to make the phrase correct.
From which part will I take the matchstick?
After guns are fired in a saloon, 75% of the cowboys have a wounded ear, 80% have a wounded eye, 85% have a wounded arm, and 90% have a wounded leg.
What is the smallest percentage possible of cowboys who have all four wounds?
After a rodeo, four cowboys have a meeting in a saloon.
Each cowboy has one 'bullet'. (Technically, the bullet is the projectile. You load a gun with a round or a cartridge.)
Each cowboy randomly chooses one of the other three cowboys and successfully shoots him.
What is the probability that all of them are shot?
The photograph courtesy of Roland Sauter
Dueling Idiots Problem: three idiots participate in a duel.
They shoot at the same time.
If each idiot randomly chooses one of the other two idiots and successfully shoots him, what is the probability that at least one idiot will survive?
This shape was formed by removing a small cube from a big cube.
The volume of the removed cube is 1/4 of the big cube's volume.
Find the surface area of the shape compared with the surface area of the big cube.
What is the probability that the next person you meet is George Washington, the first president of the United States?
John has just had a 1% net pay rise.
He used to take home $5,000 a month.
He told his wife that the rise was a third of a percent.
How much more money does he keep for personal spending this year?
A lady, attempting to avoid revealing her real age to her husband, says:
I'm twenty-two years old if you do not count weekends and one summer month of every year.
Guess her real age.
Choose the bolt head design that can be easily turned with the household wrench.
A gardener has to reach the island in the middle of a pond without getting wet.
The gardener has two planks each X feet long.
What is the smallest length of the planks?
The twins are the same height.
They place four identical blocks as shown in the figure.
How tall are the boys?
Eugenia's grandmother bought a new car for $55,000 in 1970.
The car depreciated in value 10% each year until 1990.
After 1990, it increased in value by 10% each year.
How much was the car worth in 2010?
Eugenia, the magician, receives a 50% discount every time she asks for the price.
She bought a $100 puppy for less than $1.
How many times did she ask for the price?
Only one shadow is correct in the picture. 
If you turn the piece of paper upside down, what will be written on it?
Where are the shadows cast by objects both sharper and darker?
What is the number of the parking spot covered by the red truck?
Which sign is pronounced the same as a car brand but looks different?
How many bricks does it take to complete a two storey building made of brick?
Think outside the box! 
Which two roads look the same in the picture?
How many bars are there in the picture?
Gerry had 6 eggs. He broke 2. He fried 2. He ate 2. 
What is the maximum number of pieces a doughnut can be cut into by 3 straight cuts? 
What is missing in the picture?
Which word is coded below? 
i start from O, 
What does the picture show?
There is a mistake in one of the letters. 
"300" costs $30; 
How many teeth does the Funny Man have?
Guess!
If I delete a letter in a word, then only one is left. 
Logic puzzle: 
What is the largeest number of matchsticks I need to remove to make 10?
What is the next letter in this series?
Find a phrase that differs from the others.