### Fun Facts (Hints)

Different types of riddles have challenged people for centuries, here are a few facts about them that may give you some hints in solving these challenging questions:
Riddles in math are used by math teachers in many different cultures.
Many teachers promote the idea that giving students mathematical riddles helps to encourage their pupils to think more creatively and strategically.
These riddles are considered especially helpful in classrooms where students have emotional problems, as it pulls them away from their problems, and forces them to think creatively about what is before them.
Detectives are sometimes forced to solve riddles involving math when searching for psychopaths and serial killers.
Math riddles are used at home by many parents seeking to help their students become more engaged in their math schoolwork/homework.

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## A Nose That Grows

Every time a man lies his nose grows to 150 percent of its size. Every time he tells the truth it shrinks to 50 percent of its size.

What will happen if he alternates between lies and the truth

What will happen if he alternates between lies and the truth

Hint:

For every pair of a truth and a lie his nose will shrink to 75 percent of its previous size prior to this truth and lie. So the correct answer is 0. As the number of times he tells a lie and the truth ((3/4)n) approaches infinity the length of his nose approaches 0.

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## How Many Times A Day?

Hint:

22 times: 12:00:00, 1:05:27, 2:10:55, 3:16:22, 4:21:49, 5:27:16, 6:32:44, 7:38:11, 8:43:38, 9:49:05, 10:54:33. Each twice a day.

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## A Knight To The Rescue

A knight comes to a castle where his love is trapped. The castle is surrounded by a square moat that is 10 feet wide (it forms a square around the castle). The knight is able to fashion two 9 foot long planks to cross the moat.

How can he do this?

How can he do this?

Hint:

He puts one plank across the corner of the square (where two sides meet) and puts the other perpendicular to it to form a 'T' shape in the corner allowing him to cross the moat and save his beloved.

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## How Many Batteries?

You have a flashlight that takes 2 working batteries. You have 8 batteries but only 4 of them work.

What is the fewest number of pairs you need to test to guarantee you can get the flashlight on?

What is the fewest number of pairs you need to test to guarantee you can get the flashlight on?

Hint:

7. If you break the batteries into 3 groups: Two groups of 3 and one group of 2. By doing this you guarantee that one of the groups has 2 working batteries. Both of the groups of 3 have 3 possible combinations of 2 batteries and the group of 2 only has 1 combination. So, 3 + 3 + 1 = 7 tries at most to find two working batteries.

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## Brownie Currency

You're going to a friends house and want to give them some brownies. On the way to their house you cross 5 bridges. At each bridge you must pay a toll of half of your brownies to the owner. But they are all very nice and give you back a brownie from what you give them.

How many brownies must you start with to give your friend 2 brownies?

How many brownies must you start with to give your friend 2 brownies?

Hint:

Just 2.

Each time you give the owner of a bridge half of your brownies (1 brownie) they give you one back as well.

YES NO

Each time you give the owner of a bridge half of your brownies (1 brownie) they give you one back as well.

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## Find That Tennis Ball

You have 7 tennis balls that are all identical but one of them is slightly lighter than the others.

Using a balance scale and only two separate weightings, how can you find the light tennis ball?

Using a balance scale and only two separate weightings, how can you find the light tennis ball?

Hint:

Put three of the balls on each side. If they are even the ball that wasn't weighed is the light one. If they aren't even the side that is lighter has the light ball. Of these three balls, one should be put on each side. If the sides are even than the other ball is the light one. If they aren't even the one that is lighter is the ball you're looking for.

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## The Same Birthday

How many people do you need to have the odds be in favor (at least 50% chance) of two people having the same birthday?

Hint:

## Chess Board

You have an 8 by 8 chess board that has two corner squares diagonal from each other removed. Is there any way to place 31 dominoes of size 2x1 to cover the remaining 62 spaces?

Hint:

No. When you remove the two diagonal spaces from the chess board they are both black or both white, making it so that there are two more of the other color. Each domino would cover 1 black and 1 white space. So 31 of them would have to cover 31 white spaces and 31 black spaces but with the corners removed there are 30 of one color and 32 of the other.

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## How Many People?

Hint:

9. Two twins are 2 people, three triplets are 3 people, and four quadruplets are 4 people. 2 + 3 + 4 = 9.

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## Toasting Toast

Jasmine has a toaster with two slots that toasts one side of each piece of bread at a time, and it takes one minute to do so.

If she wants to make 3 pieces of toast, what is the least amount of time she needs to toast them on both sides?

If she wants to make 3 pieces of toast, what is the least amount of time she needs to toast them on both sides?

Hint:

3 minutes. She puts two pieces in the toaster, toasting one side of each. Then she flips one of them, takes one out, and puts the completely untoasted piece into the toaster. Finally, she takes out the toasted piece and puts the two half-toasted pieces of bread into the toaster for a minute and she's done.

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## How Many Pieces Of Chicken?

A fast food restaurant sells chicken in orders of 6, 9, and 20.

What is the largest number of pieces of chicken you cannot order from this restaurant?

What is the largest number of pieces of chicken you cannot order from this restaurant?

Hint:

After 6 all numbers divisible by 3 can be ordered (because they can all be expressed as a sum of 6's and 9's). After 26, all numbers divisible by three when subtracted by 20 can be obtained. After 46, all numbers divisible by three when subtracted by 40 can be obtained. After 46, all numbers fit into one of these 3 categories, so all numbers can be obtained. 43 is the last number that doesn't fall into one of these categories (44 = 20 + 6 * 4, 45 = 6 * 6 + 9).

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## Math Class

Nathan has math 4 times a week. If he has math 8:00 Monday, 9:20 on Tuesday, 10:40 on Wednesday, and 1:20 on Friday, when does Nathan have math on Thursday?

Hint:

## Two Planes

There are two planes. One is going from New York to London at a speed of 600 MPH. The other is traveling from London to New York at a speed of 500 MPH.

When the planes meet which one will be closer to London?

When the planes meet which one will be closer to London?

Hint:

## What Are Your Chances?

If you randomly choose one of the following answers to this question, what is your chance of getting it right?

Hint:

0%. No matter which answer you choose you are incorrect. All of the answers create a logic loop.

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## How Many Children?

Mr. Smith has 4 daughters. Each of his daughters has a brother.

How many children does Mr. Smith have?

How many children does Mr. Smith have?

Hint:

He has 5 children, all of the daughters have the same 1 brother.

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## Post Your Math Riddles Below

Can you come up with a cool, funny or clever Math Riddles of your own? Post it below (without the answer) to see if you can stump our users.