ID 9971

ID 9957

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?

ID 9938

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?

ID 9914

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?

ID 9910

ID 9881

My first is in bread and butter.

My second is in home, but not in hearth.

My third is in nut, but not bolt.

Which am I?

ID 9811

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?

ID 9797

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?

ID 9796

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?

ID 9748

ID 9744

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?

ID 9735

ID 9726

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?

ID 9672

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?

ID 9650

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

ID 9636

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?

ID 9617

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?

ID 9605

ID 9592

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.

ID 9577

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?

ID 9541

ID 9532

ID 9479

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?

ID 9444

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?

ID 9438

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?

ID 9433

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?

ID 9393

About 37 million people live in the urban area of Tokyo, Japan.

Estimate how many boys there celebrate their birthday on April, 1st.

ID 9389

ID 9381

ID 9364

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?

ID 9345

A dragonfly bears two pairs of wings and three pairs of legs.

Wikipedia says that dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.

How many times does a dragonfly fly faster forward than backwards?

ID 9315

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?

ID 9313

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?

ID 9291

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?

ID 9285

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?

ID 9250

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?

ID 9222

Alice is a well-educated, law-abiding girl. She goes to her school.

Can you guess the country where she lives?

ID 9214

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?

ID 9212

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?

ID 9187

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?

ID 9178

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?

ID 9176

Gerry opens every single locker. Then he closes every second locker. Then he goes to every third locker, closing it if it is open, or opening it if it is closed.
Then he does the same with every fourth locker and so on. The process is completed with the twelfth locker.

How many lockers are open at the end?

ID 9157

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?

ID 9115

ID 9113

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.

ID 9107

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?

ID 9075

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?

ID 9066

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?

ID 9050

ID 9009

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?

ID 8995

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?

ID 8986

Father promised John 1 cent for 1 solved problem, 2 cents for 2 solved problems, 4 cents for 3 solved problems, . . .

John finished the weekend with an extra $20 and several cents in his pocket.

How many problems did he solve?

ID 8981

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?

ID 8952

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?

ID 8899

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?

ID 8861

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?

ID 8842

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?

ID 8619

ID 8600

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?

ID 8589

ID 8522

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?

ID 8518

ID 8500

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?

ID 8462

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?

ID 8422

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?

ID 8379

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'?

ID 8377

ID 8352

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?

ID 8349

ID 8303

Tricky Equation Puzzle: the equation below is wrong:

62 - 63 = 1

Which numeral has to be moved to make the equation correct?

ID 8300

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?

ID 8287

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 2022 might be named.

ID 8241

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?

ID 8216

ID 8200

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.

ID 8178

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?

ID 8079

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?

ID 8073

ID 8043

ID 8042

ID 7943

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?

ID 7853

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?

ID 7813

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*

ID 7807

FOUR + FIVE = NINE

Each letter represents a unique digit in the cryptarithm.

What is the smallest possible value for NINE?

ID 7794

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?

ID 7721

ID 7681

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?

ID 7658

ID 7649

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?

ID 7595

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?

ID 7378

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?

ID 7262

ID 7203

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?

ID 7144

ID 7079

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?

ID 7035

ID 7030

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?

ID 7025

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

ID 6998

**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.

ID 6814

ID 6810

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.

ID 6562

ID 6457

ID 6397

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?

ID 6375

Logic Puzzle

There are only X types of people:

those who understand binary and those who don't.

What number can replace X?

ID 6359

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?

ID 6316

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)?

ID 6297

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?

ID 6216

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?"

ID 6210

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?

ID 6183

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?

ID 6131

ID 6128

Number SEVEN is mystic and frequently used in human culture.

What is the most reasonable cause of that fact?

ID 6042

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?

ID 6009

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.

ID 6008

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?

ID 5992

ID 5919

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?

ID 5857

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?

ID 5837

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?

ID 5776

A rodeo began 166 minutes before 1:36 PM.

When did the rodeo begin?

The photograph courtesy of Roland Sauter

ID 5681

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?

ID 5617

Brainteaser: A word becomes shorter when you add two letters to it.

How many letter are there in the word?

ID 5458

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?

ID 5234

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.

ID 5204

ID 5185

ID 5175

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

ID 5174

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?

ID 5166

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

ID 5165

ID 5157

**Buy 2 for the price of 3 and get 50% off!**

What is the final rebate do you get?

'Buy, buy, says the sign in the shop window; Why, why, says the junk in the yard.' - Paul McCartney

ID 5152

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.

ID 5135

**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.

ID 5049

A short word can be written forward, backward or upside down while remaining the same word.

What is the first letter of the word?

ID 4989

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?

ID 4925

Anna (A), Bill (B), Cindy (C), and Daniel (D) work on a project.

(1) Together, A, B, and C can complete it in 100 days.

(2) Together, B, C, and D can complete it in 101 days.

(3) Together, C, D, and A can complete it in 102 days.

(4) Together, D, A, and B can complete it in 103 days.

Rank them from the best to the worst performer.

ID 4891

ID 4880

If you were to spell out the numbers, how far would you have to go before encountering the letter 'A'?

ID 4703

On average there are 100,000 strands of hair on a person's head.

Hair grows at a rate of about 15cm a year and each hair lasts up to 6 years before it falls out.

If two sisters have 222,222 strands of hair together, and one has 20% more hair than the other, what is correct?

ID 4664

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?

ID 4660

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?

ID 4659

95.8% of James' classmates have different numbers of hairs than he has.

How many students are there in his class?

ID 4633

ID 4610

ID 4588

Chimpanzees have 32 teeth which are very similar to those of humans which never visited dentists.

If there are 18 chimpanzees in a zoo what is the maximum possible number of their teeth?

ID 4586

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?

ID 4579

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?

ID 4576

The theory of relativity connects the mass at high speed with initial mass, the velocity of the object v, and the speed of light c.

How much heavier is a bullet that navigates at 60% of the speed of light?

ID 4574

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?

ID 4573

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?

ID 4569

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.

ID 4565

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?

ID 4542

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.)

ID 4541

Gerry's circular garden is 1200 m in diameter and has no fence.

How far can a wolf run into the garden?

ID 4527

ID 4523

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?

ID 4510

Bob used to weigh 100kg.

His new stressful job causes him to lose 10% every month.

How much does he weigh after 3 months of work?

ID 4472

Mrs. Smith has three sons who played hockey, two sons who played basketball, one of these sons played two sports, and one son who smokes and does not play any sports.

How many sons does she have?

NOTE: Smoking is harmful to your health.

ID 4436

Two trains are 1 kilometer apart on a single track railway line. They set off towards one another at 1 m/second.

A bee sitting on the front of one of the trains sets off and starts to fly along the railway line at 3 m/second.

When the bee meets the other train it immediately turns around and flies towards the first train and so on . . .

How many times does the bee turn before the trains bump into each other?

ID 4421

"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

ID 4412

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

ID 4380

ID 4338

There are 5 children in a boat.

Four of them do one of the activities below.

What is the fifth kid doing?

ID 4308

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?

ID 4306

ID 4234

Ben ate 100 bananas between Monday and Friday, stopping for the weekend.

Each day he ate six more bananas than on the previous day.

How many bananas did Ben eat on Wednesday?

ID 4214

ID 4213

Mr. Smith bought glasses for all members of his family including animals and him.

If every pair of glasses costs $10 and the tax is 8%, how much money did he spend?

ID 4212

Jane is cooking for 22 pirates.

She needs 2 eggs per pirate and at least 3 eggs for herself.

How many dozens of eggs should she bring to the kitchen?

ID 4169

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."

ID 4165

Five students Anna, Bill, Craig, Daniel, and Eugene commute by bus. Every morning each student independently and randomly selects to board one of the 4 buses.

What is the average number of students in the bus that Anna chooses?

ID 4120

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.”

ID 4037

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.

ID 4005

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?

ID 3979

How high is a $50,000 stack of $1 bills, given that the thickness of 100 bills is about 1 centimeter (0.033 feet)?

ID 3939

An aquarium has a water surface area of 10,000 cm^{2}.

I put a brick that measures 40 cm x 20 cm x 12.5 cm in the aquarium.

Estimate by how many centimeters the water rises.

ID 3938

The Smith family consists of parents, children, and animals. Some of them are absent in the picture.

The average age of the family is 22; the father is 42 years old and the average age of the others without the father is 20.

How many people and animals are there in the family?

ID 3925

In a game, Anna and Bill take 1, 2, or 3 coins on each turn.

The player to take the last coin from the pile wins.

If Anna goes first and there are 40 coins on the table, how many coins should she take to guarantee that she would win?

ID 3909

How many 1x1 squares fit into the large square with the side length 4.8?

Find the maximum possible number.

ID 3889

Job interview logic puzzle in a bank.

Which of these pieces of information would be most useful for estimating the number of people who travel in a train with 20 passenger coaches?

ID 3861

A frog ate 20 flies in a day.

Each day, the frog ate 20 more than on the day before.

In how many days did she eat 1000 flies?

ID 3852

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?

ID 3836

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?

ID 3772

Guesstimation

A man can jump up to four times the length of his own body.

Frogs can jump up to fifty times their length.

A flea can jump 350 times the length of its own body.

What is the average length of these three jumps?

ID 3760

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?

ID 3758

A committee consists of 7 people. The committee keeps an important object in a safe.

How many mechanical locks must the safe have so that it can be opened precisely when at least 4 members of the committee are present?

You may suggest your design of the lock(s).

ID 3737

I place 11 chairs along the walls in an empty rectangular room.

The number of chairs along each wall is the same.

Find the number.

ID 3727

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?

ID 3714

ID 3694

ID 3662

ID 3643

Your boss has been told to give you a medal at the end of the day, for each of the seven days you work for him.

The medals are attached to a strip. Your boss can cut the strip to separate the medals, but he is very lazy and the strip is so strong that he can only cut one strip thickness at a time.

What is the minimum possible number of cuts he has to make?

ID 3635

At a party 60% of the boys are dancing with 90% of the girls.

How many people are dancing if there are 50 people?

ID 3611

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?

ID 3610

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?

ID 3609

"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?

ID 3606

Alex(A), Beatrice (B), and Craig (C) work on a project.

(1) Together, A and B can complete it in 10 days.

(2) Together, B and C can complete it in 12 days.

(3) Together, C and A can complete it in 15 days.

If Alex does it alone, how many days will it take?

ID 3600

ID 3597

A boy has as many sisters as brothers, but each of his sisters has three times more brothers than sisters.

How many sisters are there in the family?

ID 3587

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.

ID 3583

A surgeon has two pairs of surgical gloves.

What is the maximum number of people on which he is able to operate?

NOTE:

1)There is no blood contact between the people including the surgeon.

2) The surgeon needs to use both hands for each operation.

ID 3547

A bus carrying 5 tourists travels to Dogland. Every tourist has a dog. Every dog has 5 puppies. A dog has 5 toes on each paw.

How many toes are there in the tourist bus?

ID 3545

ID 3543

A bug walks from corner A of a room to corner B by only moving along the walls.

What is the shortest path it can take?

ID 3531

ID 3518

A two-digit number, read from left to right, is 20% greater than the same number read from right to left.

What is the number?

ID 3516

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?

ID 3514

ID 3511

What is heavier than a cumulus cloud, which is about 1 cubic kilometer in volume?

Water is 1000 times heavier than the same volume of cloud.

ID 3507

I want to move just two matchsticks to make the equation correct.

How many different ways are there to do this?

ID 3506

ID 3497

Bob shaves himself 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?

ID 3492

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?

ID 3487

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?

ID 2307

ID 2306

ID 2304

I participate in a Formula 1 race.

One second before the finish I am the first who overtakes the last.

What position do I finish?

ID 2303

ID 2302

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?

ID 2301

How many apples can I place, such that the distance from every apple to every other apple is a single fixed value?

ID 2299

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?

ID 2298

152 Garfield Show episodes were produced in 2009 - 2012.

Each episode is 22 minutes.

How many days (twenty-four hours) would I spend watching all these episodes without breaks?

ID 2297

A goldfish needs 1000 cubic inches of water to live in.

An aquarium is 20 inches in diameter.

How many goldfish can live in this aquarium?

ID 2296

The national debt of a country is $16.5 trillions.

It has a population of 300 million.

If each person paid back $100 per month, how long would it take to pay off the national debt, assuming there was no requirement to pay interest?

[ NOTE: Use the definition: 1 trillion = 1 million million ]

ID 2289

Bob shaves himself 4 minutes per day.

If he lives 70 years, what is the total amount of time spent shaving?

ID 2286

ID 2273

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?

ID 2272

ID 2257

ID 2256

A group of kids with dogs go for a walk.

There are 49 feet and heads altogether.

There are more dogs than kids.

How many dogs are there?

ID 2255

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?

ID 2253

ID 2252

ID 2249

ID 2244

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?

ID 2241

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?

ID 2237

You are shrunk so that your height is equal to the diameter of a dime (a ten-cent coin) and your mass is proportionally reduced so as to maintain your original density.

Who is heavier, you or the dime?

ID 2235

ID 2234

ID 2233

On average there are 100,000 strands of hair on a person's head.

Hair grows at a rate of about 15cm a year and each hair lasts up to 6 years before it falls out.

If the population of London is 8,000,000, what is the probability that at least 2 of the inhabitants have the same number of hairs on their heads, discounting bald people?

ID 2232

ID 2227

One hundred soldiers form a 10 x 10 square.

From every column, the tallest soldier is chosen, and from these 10 soldiers, the shortest is chosen. His height is X.

At the same time, the shortest soldier is chosen from every row, and from these 10 soldiers, the tallest is chosen. His height is Y.

Compare the heights.

ID 2221

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?

ID 2219

A lot of money is in a box.

None or just one inscription on the boxes is true.

Guess where the money is.

ID 2218

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?

ID 2217

An amoeba is a shapeless unicellular organism.

An amoeba propagates by simple division into two amoebas; each split takes 3 minutes to complete.

At noon, 0.1% of a Petri dish was filled with amoebas.

At what time will the dish be full?

ID 2216

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?

ID 2214

I am selling my car. People come to my garage one at a time and make bids to buy it. I make an immediate decision whether to accept or reject an offer after receiving it. I decide to reject the first N offers, mark the highest price P, and accept the first offer that is greater than P.

What value of N do you recommend to me if I expect that 270 people will make a bid?

If N is small, I can accept a small amount of money.

If N is large, I can reject the best offer.

ID 2205

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?

ID 2195

I want to measure exactly six minutes from the moment I touch an hourglass, using only a five-minute hourglass and a four-minute hourglass.

How many times do I flip over an hourglass?

Count the initial flip(s) and find the minimum possible number.

ID 2194

ID 2192

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?

ID 2191

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

ID 2187

ID 2186

ID 2179

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?

ID 2177

Three mentors and four apprentices produce as many devices in five days as two mentors and four apprentices do in six days.

Who is the best performer?

ID 2169

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. They have the same skills and productivity, but refuse to work on the same activity at the same time.

What is the shortest project duration if they work together?

ID 2167

One hundred and thirty shareholders decide to buy 30,000 shares of company A.

They decide that five gentlemen together will buy a thousand shares, and that four ladies together will buy a thousand shares.

How many gentlemen are there?

ID 2156

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?

ID 2154

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.

ID 2150

Make 727 by using three 7s.

You can use any math operator that you would like.

How many times do you use the plus sign (+) in the expression?

ID 2099

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

ID 2083

This is a standard set of dominoes.

One domino has no spots and the greatest number of spots is 12.

If I randomly choose a domino, which number of spots has the greatest probability of appearing?

ID 2079

This shape was formed by removing a small cube from a big cube.

The side length of the removed cube is two thirds of the side length of the original cube.

What is the volume of the new shape compared with the original volume?

ID 2049

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?

ID 2045

ID 2035

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?

ID 2027

ID 2026

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?

ID 2025

A farmer puts several pigs into three pens.

None of the pens is empty.

All pens contain different even numbers of pigs.

What is the smallest number of pigs?

ID 2016

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?

ID 2015

ID 2011

In a family photo, I see 1 grandmother, 1 grandfather, 2 fathers, 2 mothers, 2 daughters, and 2 grandchildren.

What is the smallest number of people possible that are in the family photo?

ID 2000

Sixty-five students want to share 15 melons.

They decide that four boys will share a melon, and five girls will share a melon.

How many girls are there?

ID 1992

John can eat a pizza in 4 minutes.

Jim can eat a pizza in 5 minutes.

Their grandfather can eat a pizza in 20 minutes.

If two boys and their grandfather all start eating the same pizza at the same time, how many seconds does it take them to finish the pizza?

ID 1986

What is the largest possible number of pieces you can produce if you cut a round pizza by 4 straight cuts?

Note: you can move the pieces.

ID 1983

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?

ID 1980

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?

ID 1970

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?

ID 1962

What is the number of "Friday the 13^{th}" that occur in 2012 if 1^{st}January 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.

ID 1950

A frog jumps one meter 3 times, and every time he randomly chooses one of four directions (either north, south, east, or west).

What is the probability that the frog is 3 meters away from where he started?

ID 1946

In a casino on a Sunday, 90% of the visitors lost $100 each,

9% of the visitors lost $1,000 each, and

the rest won $10,000 each.

If the profit of the casino is $80,000, how many people visited the casino?

ID 1944

ID 1940

I strike a pool ball.

The picture shows the trajectory of the ball.

How many times does the ball hit the table sides before it lands in a pocket?

ID 1936

ID 1935

A county hospital proudly announces

"A new baby is born every 20 minutes, 24 hours a day, and 500 births each week."

What is the difference between the two advertised numbers?

ID 1928

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?

ID 1897

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 m^{2}?

ID 1886

Bob the plumber has 10 pockets and 60 nuts.

He wants to put the nuts in all of his pockets so that no two pockets have the same number of nuts.

What is the largest number of nuts that a pocket can possess?

ID 1862

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?

ID 1856

I want to move just one matchstick to make the phrase correct.

From which part will I take the matchstick?

ID 1833

A kitten has a 50/50 chance to be male or female.

My cat just delivered two adorable kittens.

My veterinarian said that at least one of them is female.

What is the probability that the other kitten is a boy?

ID 1832

ID 1831

Three white hens and four black hens lay as many eggs in five days as two white hens and four black hens lay in six days.

Which color hen lays the greatest number of eggs?

ID 1822

ID 1811

I would like to cut the shape into the fewest possible pieces that will fit together and form a rectangle.

What is the smallest number of pieces?

ID 1809

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?

ID 1783

After a gun is 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 greatest percentage possible of cowboys who do not have any wounds?

ID 1761

This is a standard set of dominoes.

One domino has no spots, one domino has 1 spot, and two dominoes have 2 spots.

The greatest number of spots is 12.

Which number of spots appears more frequently on the dominoes?

ID 1717

John ate a piece of a pizza and left the rest for his friends, Jim and Jack.

The diagram shows the amount of pizza Jim and Jack equally shared.

Who ate the smallest amount of the pizza?

ID 1671

After a gun is 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?

ID 1543

After a rodeo, four cowboys have a meeting in a saloon.

Each cowboy has only one bullet.

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

ID 1529

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?

ID 1520

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.

ID 1517

A dragon drank 1/5 of the water in a lake.

After a break, he drank 1/4 of the remaining water.

After another break, he drank 1/3 of the remaining water.

After a final break, he drank 1/2 of the remaining water.

How much water is left in the lake, compared with the initial amount?

ID 1493

Each box is labeled incorrectly.

I want that the boxes are labeled correctly.

I can open only one box.

Which box should I choose?

ID 1479

The diagram shows 15 billiard balls that fit exactly inside a triangular rack.

The rigid rack prevents the balls from sliding.

What is the largest number of balls that can be removed so that the remaining balls are theoretically unable to move?

ID 1377

What is the probability that the next person you meet is George Washington, the first president of the United States?

ID 1313

With the cash in her pocket, Mrs. Smith can either exactly afford ice cream cones for all her family including the baby and animals OR one huge cigar for her beloved husband John. The cigar would cost $14.

Find the price of an ice cream cone.

NOTE: Smoking is harmful to your health.

ID 1310

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?

ID 1151

On January 1st, Anna and Bill have $100 each.

Each month Anna saves $10 more than she spends while Bill spends $5 more than he saves.

At the beginning of what month is Anna 10 times richer than Bill?

ID 1116

In a game, you have a 1/5 probability of winning $100 and 4/5 probability of losing $26.

What is the most likely amount of money you will win (or lose) at the end of 1000 games?

ID 1110

ID 1055

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.

ID 1011

ID 976

A gardener has to reach the island in the middle of a pond without getting wet.

The gardener has two planks each X meters long.

What is the smallest length of the planks?

ID 941

The twins are the same height.

They place four identical blocks as shown in the figure.

How tall are the boys?

ID 932

ID 917

A girl was born in the 20th century.

Take away from her year of birth the sum of the four numerals that make it up.

You will end up with a number divisible by X.

Find X.

Source: Berrondom, Marie Mathematical Games, 1983

ID 746

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?

ID 659

I strike a pool ball from corner A of the rectangular billiard table at an angle of 45°.

Into which corner pocket will the ball fall?

ID 653

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?

ID 477

The Chinese Calendar is based on a twelve-year cycle.

Each year in the cycle corresponds to an animal:

Tiger, Rabbit, Dragon, Snake, Horse, Sheep (or Goat), Monkey, Rooster, Dog, Pig, Rat and Ox.

The order of the animals never changes.

The year 2010 in the Chinese calendar is the Year of the Tiger.

Which animal will mark the year 2110?