A loaded truck weighs between 4 and 5 tons.
How many tons would 45 trucks weigh?
John put $10,000.00 in a savings account at an annual interest rate of 4%. He pays 25% tax on earnings.
How much will he have in 1 year?
In 2000, the population of a small town was 10,000 residents.
If the annual rate of increase was 1% in 2001 and -1% in 2002, what was the population at the beginning of 2003?
In a basketball tournament, a team must be defeated twice to be eliminated. There are no draws.
Eight teams participate in the tournament.
What is the largest number of games that can be played?
It costs $24 to paint a cube, the cost being proportional to the surface area.
Before painting, it was cut in two pieces by a plane.
What is maximum possible cost to paint these two pieces?
A full box with 100 matches weighs the same as two boxes with 40 matches each.
How many empty boxes weigh the same as a full box?
The cross-section of the identical arc stones is a trapezoid with three equal sides.
Find the smallest angle of the trapezoid.
The diagram shows a road network.
All cars drive in one direction from A to B.
The numbers represent the maximum flow rate in vehicles per hour.
What is maximum number of cars that can drive through the network every hour?
I would like to rearrange the items in the six bins shown on the right to decrease the number of bins in use.
What is the smallest number of these bins that can be used?
To paint four solid white lines and two dashed white lines costs $999.00 per 1 kilometer.
The dashed line is 4 times less expensive than the solid line.
If we increase the number of lanes from 2 to 5 in each direction and separate them by the dashed lines, how much would the cost increase?
Benny Bunny starts jumping from a hole.
Every leap is two times longer than the previous one.
Does Benny have a chance to come back to the hole?
Three boys want to equally share three pancakes.
The picture shows the pancakes' diameters.
Which part of the largest pancake will one of the boys receive?
If 10% of the people get 90% of the total salary paid in a county, and the average salary is $50,000, what is average salary of the highest paid people?
What is the number of "Friday the 13th" that occur in 2012 if 1stJanuary is a Sunday?
Note: April, June, September, and November each have 30 days, February has 29 days, and all the other months have 31 days.
A total of 321 employees work for company XYZ and two thirds of them are men.
To obtain a workforce in which one third are men, how many women should be hired?
Bob is paid $5,000 a month for his regular job.
During Summer holidays, he reviews books, gives public speeches, and earns an additional $15,000 from his second job.
What percent of his annual income does Bob earn from his second job?
The business of company A is 10% greater than the business of company B now.
In ten years, company B will be 50% bigger than it is now and company A will be 10% smaller than company B.
How much faster will company B be growing than company A over the course of these ten years?
John is going to repair his house. There are three major activities:
electrical installation takes 3 man-days;
sanitary installation takes 4 man-days; and
garden work takes 5 man-days.
His neighbor Mary agrees to participate in the project. She works two times faster, but refuses to work on the same activity with John at the same time.
What is the project duration if they work together?
The picture shows a simplified statement of income for company ABC in million.
How does the profit change if the revenue decreases by 10% and the expenses increase by 10%?
I have a rectangular piece of cheese with a round hole.
What line cuts the piece of cheese into two parts of equal weight?
I place 1000 coins in two columns in a wooden box, and they fit nicely as shown.
How many more coins can I place into the box if its width is increased by 30%?
There are 135 cars in a village of 30 families.
Each family has either 4 or 5 cars.
How many families have 5 cars?
It costs $27 to paint a cube.
Before painting, we divide the cube into two rectangular boxes.
How much will it cost to paint these two boxes?
A $10 million lottery pot is divided into equal increments over 25 years. The government retains 35% of the total for taxes.
How much could the winner expect to receive after taxes each year?
If three students eat three apples in 40 seconds, how long will it take six students to eat 17 apples?
NOTE: They do not cut the apples into small parts.
John works 5-hour shifts at a call center.
He earns $5 per hour and $5 per call.
How many calls does he need to receive per shift to earn a total of exactly $500 in 5 shifts?
A taxi company charges $1.95 for the first mile and 50 cents for each additional mile.
What is the maximum distance someone could travel with seven dollars?
A bicyclist pedals downhill at 25 km/h (kilometers per hour) and uphill at 10 km/h.
It takes 2 hours to travel from a Swiss mountain village to another village.
The return trip takes 5 hours.
Find the distance between the two villages.
You have 27 dimes; 26 are real and one is fake.
All the real ones weigh the same, and the fake weighs less than the real ones.
How many times do you use a balance scale to find the fake dime?
A city hall floor is to be tiled in the following pattern.
The hall measures 100 x 100 tiles.
How many green tiles do we need?
A restaurant sells a 30 cm (in diameter) pizza for $9, while their large 40 cm pizza is specially priced at $14.
What is the percent discount the restaurant is offering for the large pizza?
A real estate agent receives a 5% commission on the selling price of a house from the buyer.
You can borrow 65% of the house price from your bank.
If you have $200 000, what is the most expensive house that you can afford?
A real estate agent receives a 5% commission on the selling price of a house from the buyer.
You can borrow 75% of the house price from your bank.
If you have $360 000, what is the most expensive house that you can afford?
In a casino on a Sunday, 90% of the visitors lost $200 each,
9% of the visitors lost $1,000 each, and
the rest won $10,000 each.
If the profit of the casino is $340,000, how many people visited the casino?
In a survey of customers, 2/3 of the female clients and 3/4 of the male clients preferred using antiglare display computers over glossy display computers.
Women make up 48% of the clients in the region.
What percent of the clients prefer to use antiglare display computers?
A girl begins to ascend a mountain from its base at 8:00.
She follows a track, makes stops, and arrives at the summit at 19:00.
On the next day, she begins her descent at 8:00 and follows the same track downhill to arrive back at the same place at 19:00.
Is there a spot along the track that she visited at the same time on both ways?
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?
Bill is going to visit his family in New York.
He lives 105 miles away in Connecticut.
He can travel at an average speed (on departure) of 50 miles / hour (mph), which constantly decreases to 10 mph on arrival.
What time should he leave if he needs to meet his family at noon?
How many 1x1 squares fit into the large square with the side length 3.7?
Find the maximum possible number.
A group of 24 scouts goes on a trip.
They prepare enough food to last 10 days.
If 6 additional scouts join them at the last minute, how many days will their food last?
Water weighs 1000kg per cubic meter at 4 degrees Celsius.
Fresh snow that melts into water becomes approximately 1/10th its original volume.
Estimate the snow weight on the roof of a house if the roof width, length, and height (pitch) are 9.6 meters, 10 meters, and 2 meters, respectively.
The height of the snow is 1 meter.
In 2013, 87.5% of Swiss train passengers arrived at their destination with no more than a three-minute delay.
If there are 8 million people live in the country and one-eighth of them take the train every day, how many passengers were late in 2013?
The heights of the masts from the first to the fifth are 32 m, 36 m, 35 m, 32 m, and 26 m.
They are 8 m apart.
What is the maximum distance between two neighboring tops?
John buys a car, paying 20% in cash.
The rest of the amount is paid by a special interest-free loan.
He pays $1,680 a month for 5 years.
Find the total amount paid for the car.
In a company all people except “shop workers” have 2 direct subordinates.
How many shop workers are in the company if there are 10 levels of subordination within the company?
The State Tennis tournament starts with 128 players.
How many rounds must be played before a champion is found?
A solid metal ball weighs 9 pounds.
How much will another ball of the same metal weigh if its diameter is twice as long?
Items accepted by an airline must not be more than 3 x 4 x 12 ft long.
What is the largest flute can I take with me?
According to USDA's Economic Research the average American ate 2000 lbs of food in 2011, about 1000kg or the weight of a small car.
If the average Indian eats 5 times less than an American, how much does an Indian eat in a day?
The straight road of 40 km long is divided into three different parts.
The length of the middle part is 10 km.
What is the distance between the centers of the outer parts?
A girl caught her first fish after 30 minutes of waiting.
She caught each next fish 2 minutes faster than the previous one.
How much time does it take to catch a dozen fish?
Seven trees are planted in a park, with exactly 3 meters between each successive planting.
In other words the second tree is 3 m from the first tree.
The third tree is 3 m from the second tree and so on.
What is the minimum possible distance between the first and the seventh trees?
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
What is the most money you can have in $1, $2, $5, $10, $20, and $50 bills and not be able to make exact change for a $100 bill?
Source: The Little Book of Big Mind Binders by Scott Kim
Americans measure the temperature in oF.
Europeans measure the temperature in oC.
The formula to convert Fahrenheit to Celsius is:
c = 5 (f - 32) / 9
where / is the symbol for division,
f represents the temperature in oF and
c represents the temperature in oC.
What is the temperature at which the Celsius and Fahrenheit readings are the same?
The size of most credit cards is 85.60 x 53.98 mm ( 3 3/8 x 2 1/8 in ).
Estimate the area of a card.
1 cm = 10 mm
A very old car takes 2 hours 48 minutes to get to my granny's house, 84 km away.
How long would it take at this speed for me and Jane to go to a party in the city center tonight, 12 km away?
Two automobiles set off at the same time, one from Vevey and the other from Lausanne, and arrived at Geneva at the same time.
The distance between Lausanne and Geneva is twice the distance between Lausanne and Vevey.
If the first car traveled through Lausanne without stopping, how much faster was it going than the second car?
A driver's eyes are about 1.3 m above the ground, while the hood is 2 m in front of him and 0.8 m above the ground.
What is the minimum distance in front of the hood an object on the ground can be visible?
Gerry drives to Jane's house at 60 miles per hour and comes back at 40 miles per hour.
How far from Jane's house does he live if the entire trip takes 2 hours?
How many revolutions did the Earth make around its axis in 20th century?
The 20th century was a century that began on January 1, 1901 and ended on December 31, 2000. It was the tenth and final century of the 2nd millennium.
Ten men met at a conference.
It took 4 seconds for each man to shake hands with a guy and 3 seconds to move to another one.
How long did the procedure last?
There were 196 countries on the Earth in 2010.
The 2-letter codes are supplied by the ISO ( International Organization for Standardization) for each country. For example,
US - United States,
GB - United Kingdom,
AU - Australia,
. . .
How many more new countries can get a 2-letter code?
My bath has two taps and a plug hole.
The cold tap on its own fills the bath in 18 minutes, the hot one in 24 minutes.
The plug hole can drain the bath in 15 minutes with the taps off.
How long will the bath take to fill if I leave both taps on with the plug left out?
I picked an integer from 1 to 1000.
What is minimum number of questions, with my Yes-No answer, that are needed for you to guarantee to identify the number?
Jane purchased a house for $ 400,000.
She wants a Real Estate Agent to sell it for her.
The Agent must make a commission of exactly 5% in addition to Jane's 10% profit.
How much must the Agent sell the house for?
A short word can be written forward, backward or upside down while remaining the same word.
What is the first letter of the word?
Leslie Green asks:
"Endocrinic Igorosis is a horrible disease with a 100% mortality rate for the infected. Even after 5 years nobody knows how it spreads. The fatality statistics have been steady at 100 people per 100,000 of the population every year. A remarkable cure has been found which is 100% effective at curing the disease, but only if administered before any symptoms are visible. Sadly, if the cure is given to anybody who is not infected then 3% of them will die. The latest test is 100% effective at finding this awful disease, but has a false positive rate of 5%.
How do we save the greatest number of people?"
Gerry has $30 in pennies, nickels, dimes, and quarters with proportion:
25 : 10 : 5 : 1
How many quarters does he have?
Penny = 1 cent.
Nickel = 5 cents.
Dime = 10 cents.
Quarter = 25 cents.
Martin has ten thousand dollars in the Mad Money's bank account. The interest rate for his account is 100% every year.
How much money will he have in his bank account after five years?
Granny is making a cookie for each of her 12 children, her 28 grandchildren, her beloved husband and herself.
She can make three cookies per two minutes on average.
How much time does she need to reserve for the preparation?
Leslie Green asks:
Bethany throws a hard ball at John when they are in the park and it hurts. When they are weightless in the space station she somehow manages to throw the same ball at the same speed at John.
What is the result?
Jane has a 5-liter bucket with 3%-fat milk and 3-liter bucket with 5%-fat milk.
What is the fat concentration in the milk if she pours both into a large bucket?
The 52-page newspaper "The Daily Dog News" consists of double sheets. Edgar chooses one of these sheets at random.
If one page number is 10, what are the three other page numbers of the sheet?
Lottery 6-digit numbers are from 000001 to 999999. A ticket is considered to have a “special” number if the sum of the first 3 digits is equal to the sum of the last 3 digits.
Find the sum of digits of the smallest possible special number.
No digit is used twice in the six digit number.
Gerry ate lunch at a restaurant. The bill came to $28.
If he left a 20% tip, what was the total cost of his lunch?
A dime has a mass of 2.27 grams. A nickel has a mass of 5 grams. Jane has a bag of dimes and a bag of nickels. Both bags of coins have the same mass.
What is the smallest possible number of coins in the first bag?
Given that January 1st, 2016 fell on Friday, which day of the week will occur most frequently in 2016?
Note: 2016 is a leap year.
There has long been disagreement as to whether the Nile or the Amazon is the world's longest river.
If the Nile in Africa is 6853 km long and the Amazon in South America is 6992 km long, how much longer is the Amazon than the Nile?
A black hen lays an egg every fourth day.
A white hen lays an egg every sixth day.
If they both laid eggs on Monday, what is the next day they both will lay eggs together?
The knight jumps either 2 squares vertically and 1 horizontally, or 2 squares horizontally and 1 vertically, as shown in the picture.
What is the minimum number of moves the knight needs in order to go from square a8 to the square h1?
Mrs. Greedy refuses to use electricity and bought 200 candles for the next year.
She burns one candle every evening and always makes one new one from the remaining wax of seven burnt candles.
For how many days will she be able to use the candles?
The Glorioustown municipality has decided to put a paved path around Glorious Park.
The craftsmen use cubic stones. The cube side length of 0.15m includes the gap between the stones. The dimensions of the rectangular park are 300m x 600m.
If the path is to be 20 stones wide, how many stones are needed?
The typical human blink is 200 milliseconds.
Generally, between each blink is an interval of 2–10 seconds.
What is the most probable number of Jane's blinks today if she sleeps 8 hours?
Jane would ordinarily like to drive at 60 mph on this particular stretch of road. However there is a large truck driving at 30 mph which is slowing her down. She knows that in 1 mile there will be a multi-lane road section (dual carriageway) where she can easily overtake, so she waits behind the truck. Gerry is impatient and overtakes both Jane and the truck to travel at 60 mph.
Roughly how much time does Gerry save in this situation?
Author: Leslie Green
Gerry can walk at a rate of 16.8 km in 2 hours 20 minutes.
How far can he walk in 1 hour 30 minutes?
A rodeo began 166 minutes before 1:36 PM.
When did the rodeo begin?
The photograph courtesy of Roland Sauter
The formula for converting a Celsius temperature (C) to a Fahrenheit temperature (F) is given by
F = (9/5) x C + 32
There is a simple approximation: You double C and add 30.
If the temperature varies in the range from -20°C to +20°C, what is the Celsius temperature when the approximation is the worst?
The picture shows a project plan. Arrows indicate where an activity must be finished before the next activity can start. The number shows the duration of the activity in days. An activity is critical if a delay by 1 day delays the whole project.
How many critical activities are there?
Leslie Green asks:
"The History of Art in the Dark Ages is an epically boring subject and too many students pass by simply answering the 100 multiple choice exam questions randomly. This year the marking scheme has been changed so that of the 4 possible answers, the correct answer scores one point, two wrong answers score 0, but the remaining stupid answer scores minus two points.
What is the optimum strategy for a student who is good at Mathematics, but not Art History?"
Gerry scored 40, 25, 29, 35, and 31 points in the first 5 games of the season. He is aiming to score 30 points per game for the season.
How many points does he need to score in his next game to achieve this?
Leslie Green asks
"My dog Charlie rushes into my office and bumps with his nose into a book on the floor at the position shown by the blue arrow.
Describe what happens."
Gerry's granny cooks a dozen of her delicious biscuits every day.
She starts on Monday morning, while Gerry and Jane together eat 15 biscuits for lunch from Wednesday.
When are there no biscuits anymore for the first time?
I paid $15 instead of $20 buying coconuts on sale.
If I threw away 25% of the coconuts due to bad quality, how much do I gain or lose choosing the product on sale?
The mathematics department at a school has challenged the pupils to a sort of ‘tug of war’ contest. The staff pull in the direction marked M. The boy students pull in the direction marked B, and the girls of course are G. The ropes are connected together by a fairly large strong equilateral triangular plate. The ropes are attached to the plate on smooth posts so the ropes are free to swing around the pivot. The relative strengths of the pulls and the position of the plate are shown at a particular moment in time.
What happens next?
Author: Leslie Green
Susan holds a pencil completely underwater at a 45° angle to the horizontal plane. Pencils have an average density less than that of water.
What happens when she carefully releases the pencil?
Author: Leslie Green
We are going to model the growth of a particular type of bacteria as follows: No growth below 3°C. Doubles in quantity every 20 minutes for temperatures between 10°C and 60°C. Dead at 80°C.
Compare the amount of dead bacteria in two similar portions of food, one of which is left to stand at room temperature for 2 hours, then quickly heated to 80°C, whilst the other portion is immediately heated to 80°C. The initial bacteria populations in the two portions are similar at the start of the day.
Author: Leslie Green
Febe, the highly intelligent house fly, is bored buzzing around the kitchen so she hitches a lift when her Hoomins take a trip in their car. Being highly intelligent she can read the speedometer and convert the mph reading into m/s. She quickly becomes bored in the car and decides to fly directly from one side of the car to the other when the car is traveling in a straight line at 4 m/s.
Being a mathematics prodigy, she realises that her speed relative to the ground is 5 m/s.
How fast is she flying across the car?
Author: Leslie Green
For no clearly explained reason I am standing on a set of bathroom scales in a lift within a tall building. When the lift is stationary I weigh 41kg. When the lift moves I see my weight increase to 60.5kg.
Describe the motion of the lift:
Author: Leslie Green
Alex, Betty, and Craig go to the city library every fourth, fifth and sixth day correspondingly.
If all three have visited the library today, who will be together in the library next time?
3/4 of the boys and 5/6 of the girls of tenth graders participated in a party.
What fraction of the total number of students took part in the party?
A banker forgets which key fits in which of four keyholes.
What is the minimum number of trials needed to guarantee to identify which key is meant for each lock?
A jeweler has 18 pieces of chain, each with two links. He wants to make one big closed necklace of them. To do this he has to open some links and close them afterwards.
What is the smallest number of links he has to open?
The length of the Earth's day is 23 hours 56 minutes.
The length of the Mars day is 24 hours 37 minutes.
Estimate how much the Mars day is longer.
Alex has 54 Swiss francs, Peter has 49 Euros, and John has 52 dollars.
If 1 dollar equals 0.95 Euros, and 1 Euro equals 1.08 Swiss francs, who has the largest amount of money?
Pinocchio’s fortune is $1,000,000.
Each time he tells a lie to the tax inspector his fortune becomes twice less as it was before.
After he has told 10 lies, how rich is the brave man?
Calendar dates are written in different ways according to countries and preferences. For example 21 February 2018 could be written 21/02/2018, 02/21/2018, 21 Feb 2018, and so on.
You want to label filenames on a computer so that the date code is easily and automatically sorted into date order by the operating system (regardless of the date the file was actually written).
What is the correct format?
Y is a year number; M is a month number; D is a day number.
Notice that we have to put leading zeros in the each section when necessary, so we have to write 02 for the month and not just 2, otherwise the date-ordered listing is incorrect.
Author: Leslie Green
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)?
Jane is a secret agent in hostile territory. She can swim at 1m/s in still water with the secret load she is currently carrying. She has to cross a river speedily, without exhausting herself, so she swims at her normal pace. Sadly the river is flowing at 3 m/s and is 30m wide at the point she needs to cross.
How long does it take her to cross the river?
Author: Leslie Green
Perhaps you have seen birds flying, without flapping their wings, and yet they still go up.
Pick a plausible explanation for this observation.
Author: Leslie Green
Image source of the short-toed snake eagle is Wikipedia
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?
There are a few more than one thousand students in a school.
If 48% of the students are girls, how many boys are there in the school?
All the balls hanging from the balance have the same weight. The dotted suspension lines represent stretchy string, whereas the solid lines are inelastic cord.
The grey balls are possible positions for balls of equal weight to the red balls.
Which single position for a grey ball balances the beam?
Author: Leslie Green
Jason, whilst out for a drive in his front-wheel-drive car, comes across a slightly larger car stuck in mud. Jason's tow rope is long enough that Jason's car can stay on firm ground.
What is the optimum place for the rather heavy-set (large) passenger of the stuck car.
Author: Leslie Green
A company sells silk socks for $10 a pair. To produce each pair, the company spends $4 in materials and $3 in labor. The monthly operating/marketing costs are $400,000.
If they sell 200,000 pairs a month, what is the monthly profit?
Elephants eat roughly 10 percent of their bodyweight in food every day.
If the father weighs 3,600 kg (nearly 8,000 lbs), how much food does a zoo need to provide to him, if the zoo's director wants to capture and keep him for 1 year.
1 ton = 1000 kg
The average mass of an ant is approximately 0.003 grams = 3 x 10-6 kilograms.
The average mass of a bush elephant is approximately 6 x 103 kilograms.
About how many times more mass does an elephant have than an ant?
The weight of CO2 linked to the production of a 1-ton new car is about 15 tons.
If the emission of CO2 of the car is 100 g/km and it is driven 150,000 km, how much greater is the weight of the CO2 linked to owning the car compared to its weight?
For this question we don't count the emissions caused by recycling the car at the end of its working life.
1 kg = 1000 g
1 ton = 1000 kg
In a scene from a film, the baddy is sharing the ill gotten gains with his (comically stupid) henchman by dividing the gold pieces into two 'equal' piles.
'That’s one for you, and that’s one for me'.
'That’s two for you (puts an additional one on the henchman’s pile), and two for me (puts an additional two on his own pile)'.
'That’s three for you (adds one to the henchman’s pile), and three for me (puts three more on his own pile)'.
The final round is 'fifty for you, and fifty for me'.
How many fewer pieces of gold does the henchman get?
Leslie Green suggested the problem for Aplusclick project. This theme has been repeated at least once. An early version was with Bugs Bunny, 'Racketeer Rabbit' (1946).
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 21cm?
A chess king is standing on the center square of a 25×25 square tiled board. From the initial square he moves to a square sharing a common side. He steps to the north first. Moving along a 'spiral', he always tries to turn right if it is possible, otherwise he makes a straight move. He never visits a square for the second time.
How many times does he turn right before visiting all of the squares?
Jane walked a distance of 0.15 miles to Gerry's house.
When she calculated her speed in miles per hour (mph) it was exactly the number of minutes she walked.
How much time was it?
Five gentlemen ran in an election.
The winner with 22% of votes beat his opponents by 1, 2, 3, and 4 votes, respectively.
How many votes did he receive?
A boy, a girl and a dog are walking on a 10-mile circular route.
Simultaneously, the boy starts his journey clockwise and the girl and the dog starts walking in opposite direction: the boy at 4 mph, the girl at 2 mph, and the dog runs back and forth between them at 6 mph.
Where is the dog and in which direction is he facing in 91 minutes of the journey?
A boy, a girl and a dog are walking on a 10-mile circular path.
The boy starts his journey clockwise, whilst simultaneously the girl and the dog set off in the opposite direction. The boy walks at 4mph, the girl walks at 2mph, and the dog runs back and forth between them along the path at 12 mph.
How far does the dog run until all three meet?
The boss insists that the new car design must accelerate equally quickly from 20mph to 30mph as it does from 50mph to 60mph.
What is your response?
Author: Leslie Green
A physicist with broken legs is stuck in the middle of a frozen lake. For no clearly stated reason she is sitting on a smooth based sled, with a box full of base balls. We consider that the ice is perfectly flat and has low friction. Her only means of propulsion is to throw baseballs.
What is her optimum strategy to reach the edge of the lake?
Author: Leslie Green
The diameters of the wheels are 0.7m and 3.6m.
Each wheel has a silver spoke.
At a certain moment, the spokes of both wheels are at their highest points.
How many times does the small wheel turn until both spokes are at the same places for the first time again?
Each of the paths in a park is 10 meters long.
Gerry walks from A to B without going along any path more than once.
What is the length of the longest route he can choose?
During a rainstorm, 12 liters of water fell per square meter.
By how much did the water level in the outdoor pool rise?
1 liter = 1,000cm3
1m = 100cm
If the bulldozer moves 1 foot forward to the right, what happens with point A marked on the track?
1 foot = 0.3048 meters
Evguenia and her friend have enough food for a 15-day hike from Venice / Italy to the summit of Eiger in Switzerland.
How long will the food last if a foodless pal joins the team?
Leslie Green asks:
A large sofa manufacturer seems to be forever having sales. There is the Spring sale, Summer sale, Autumn sale, Winter sale, Xmas sale, New Year's sale, and so on. During these periods they sell particular lines for half price.
According to local legislation (Laws) these items have to have been offered at the higher price for a certain time and must revert to the higher price after the sale.
Assuming they stick to the legal requirements, are you getting an excellent bargain during the sales?
The image shows the cross-section of a simplified electrical water heater. The insulation is so good that we shall consider it to be perfect.
Water flows through the heater at a constant rate. Electrical power is supplied at the constant rate of 1kW.
The system is left to reach equilibrium. How much heat is absorbed by the outgoing water?
Author: Leslie Green
Estimate how much it costs to flush the toilet at home given the following:
(1) we only consider the incremental cost, not the fixed costs
(2) water supply cost is £1.5373 per cubic metre (as measured by the water meter)
(3) sewerage services cost £1.6594 per cubic metre (and are estimated as 90% of the supplied water quantity)
(4) a "standard flush" is 6 litres according to manufacturer's installation instructions.
Remember that 1 L = 1000 cm3
The British pound (GBP, £) is just another decimal currency so £1.00 = 100p
by Leslie Green
Jane's suitcase is the 8th suitcase in a line counting from the left.
Gerry's suitcase is the 7th suitcase in the line counting from the right.
There are 3 suitcases between them.
How many suitcases are there?
Gerry travelled at 120 km/h for 90 minutes and then travelled at 90 km/h for 120 minutes.
How far did he travel?
The speed limit is 120 km/h in Switzerland.
Leslie Green asks:
When painting a room with a paint brush, in which direction should a right-handed painter proceed?
Hint: consider also painting at height and older painters.
A submarine travels at 40mph (65 km/h or 35 knots) while submerged, but twice as slow on the surface.
If the total distance is 1,200 miles and it travels only 20% on the surface, what is the average speed?
The value of a computer depreciates evenly over five years for tax purposes (every year it is worth less by the same amount, so that it is worth $0 after five years).
If it was bought for $2,200, how much will it be worth after 3 years?
The satelite picture shows Great Britain, also known as Britain, that is a large island in the north Atlantic Ocean off the northwest coast of continental Europe.
What can you say with certainty about the length of its coastline?
by Leslie Green
Leslie Green asks:
You are unlikely to have seen these things before, but this is the debris from a domestic repair job. (The 1 foot ruler is just to show the size of the parts.)
But can you guess what was being repaired?
Elapsed time can get quite messy for computers to deal with.
How would you write 1 hour 23 minutes and 30 seconds as decimal minutes?
by Leslie Green
A construction firm estimates that 100 people working 1,000 hours each are able to build a new lighthouse.
Estimate how many people working full-time are required to build the lighthouse in two years.
A man who lives half way up a mountain wishes to exercise his dog by throwing a bean-bag for the dog to fetch. For the sake of simplicity, consider the mountain as conical and relatively featureless in his immediate vicinity.
Which is the optimum direction to throw the bean-bag to maximise the exercise given to the dog?
by Leslie Green
A certain medicament has a half-life of three hours. This means that every
three hours, half of the amount of the medicine is available in the bloodstream.
A patient receives 640mg of the medicament at 8:00 am
How much of the medicament remains at 8:00 am the next day if no more medicament is introduced?
Which of the following could be indicative of a successful business? 
How many boxes measuring
1 x 2 x 3 can be packed into a container measuring 5 x 6 x 7?
How many chain links do I need to produce a 2.4-meter chain? 
Where is the center of gravity (center of mass) of the orange shape?
Find the best deal.
Estimate the average width of the lake shown on the right.
You are driving your mother's car home. 
A shopkeeper of a Dairy stands six feet tall and wears size 13 sneakers. 
In how many ways can Jane put two eggs into the package? 
Where is the speed of sound the smallest? 
How many parts like the shape shown in the picture are needed to form a circle?
Which part of the balance goes down if the two weights are equal?
Which is warmer?