### Fun Facts (Hints)

Mathematics has an extensive history in just about every culture or civilized society known to man. Listed below are some cool facts to get those math juices flowing:
In 1852 mathematician JJ Sylvester established the "theory of algebraic invariants."
In 1995 math great Andrew Wiles, proved "Fermat's Last Theorem."
The first decimal number system is said to have been invented in Ancient Egypt around 5000BC.
The Ancient Mayan civilization located in Central America is one of the only cultures in the recorded history of the world to use a place-value number system.
The American Mathematical Society was formed in the late months of 1888 in New York.

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Riddles and Answers © 2017

This collection compiled by our staff on a regular basis will provide you with a great way to workout that math brain power, and will hopefully benefit you in your studies.

This is an awesome collection for anyone ages 5 and up, and contains a comprehensive set of riddles related to math for a wide range of audiences.

How many of these convoluted math riddles do you think that you can solve? Try out our collection, and be sure to come back regularly to solve our newly added math brain teasers.

## The Weight Of A Melon Riddle

Watermelon is 99% water. I have 100 pounds of watermelon. After a week, drying in the sun, the shriveled watermelon had only dried down to being 98% water. What is the total weight of the watermelon now?

Hint: We are to determine X the total mass of melon after the drying.
The Dry weight, DW is 1lb both before and after the drying.
The New Water weight, WNW is clearly X - DW or X - 1

## A Lady Steals $100

How smart are you?.....A lady walks in the store and steals $100 bill from the register without the owners knowledge. She comes back 5 mins later and buys $70 worth of goods with the $100 bill. The owner gives her $30 in change, how much did the owner lose????

A. $30

B. 70

C. $100

D. $130

E. $170

F. $200

DO NOT OVER THINK IT!

A. $30

B. 70

C. $100

D. $130

E. $170

F. $200

DO NOT OVER THINK IT!

Hint:

The best answer from the choices is the owner lost $100. The $100 bill that was stolen was then given back to the owner. What the owner loses is the $70 worth of goods and the $30 in change, which makes for a total of $70 + $30 = $100. The owner has lost $100.

Technically, the owner lost $30 plus the value, V, of the $70 of goods. Since stores typically sell goods at a markup, the value may be less than $70. But in the case of a loss leader, the owner may have lost more than $70.

YES NO

Technically, the owner lost $30 plus the value, V, of the $70 of goods. Since stores typically sell goods at a markup, the value may be less than $70. But in the case of a loss leader, the owner may have lost more than $70.

*Did you answer this riddle correctly?*YES NO

## Prince Age Riddle

A princess is as old as the prince will be when the princess is twice the age that the prince was when the princess's age was half the sum of their present ages.

What are their ages?

What are their ages?

Hint:

Current Future Past

Princess x 2z (x+y)/2

Prince y x z

I then created three equations, since the difference in their age will always be the same.

d = the difference in ages

x y = d

2z x = d

x/2 + y/2 z = d

I then created a matrix and solved it using row reduction.

x y z

1 -1 0 d

-1 0 2 d

.5 .5 -1 d

It reduced to:

x y z

1 0 0 4d

0 1 0 3d

0 0 1 5d/2

This means that you can pick any difference you want (an even one presumably because you want integer ages).

Princess age: 4d

Prince age: 3d

Ages that work

Princess:

4

8

16

24

32

40

48

56

64

72

80

Prince:

3

6

12

18

24

30

36

42

48

54

60

YES NO

Princess x 2z (x+y)/2

Prince y x z

I then created three equations, since the difference in their age will always be the same.

d = the difference in ages

x y = d

2z x = d

x/2 + y/2 z = d

I then created a matrix and solved it using row reduction.

x y z

1 -1 0 d

-1 0 2 d

.5 .5 -1 d

It reduced to:

x y z

1 0 0 4d

0 1 0 3d

0 0 1 5d/2

This means that you can pick any difference you want (an even one presumably because you want integer ages).

Princess age: 4d

Prince age: 3d

Ages that work

Princess:

4

8

16

24

32

40

48

56

64

72

80

Prince:

3

6

12

18

24

30

36

42

48

54

60

*Did you answer this riddle correctly?*YES NO

## 2 4 12 48 240 Riddle

Hint:

240. To get the number, multiply the previous number in the series by its position. 48 is in the 5th position, so 48 ï¿½ 5 = 240

YES NO

*Did you answer this riddle correctly?*YES NO

## Missing Dollar Riddle

Three guests check into a hotel room. The clerk says the bill is $30, so each guest pays $10. Later the clerk realizes the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn't know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 for himself. Each guest got $1 back: so now each guest only paid $9; bringing the total paid to $27. The bellhop has $2. And $27 + $2 = $29 so, if the guests originally handed over $30, what happened to the remaining $1?

Hint: Make a list of all of the people involved and how much money they ended up with/spent.

The $9 paid by each guest accounts for the $2 that went to the bellhop. So rather than adding $27 to the $2 kept by the bellhop, the $27 accounts for the bellhops money. The $27 plus the $3 kept by the guests does add up to $30.

YES NO

*Did you answer this riddle correctly?*YES NO

## Carton Of Eggs Riddle

There is a carton of 6 eggs on a table and there are 6 people round the table. Everybody takes an egg and there is still one in the carton. How is this possible?

Hint:

5 eggs are taken by the first 5 people, then the 6th person takes the egg , while its still in the carton!!

YES NO

*Did you answer this riddle correctly?*YES NO

## Finding The Value Riddle

Can you solve the equation by finding the value of

1. Horse

2. Cowboy boot

3. Horseshoe

4. The last equation.

1. Horse

2. Cowboy boot

3. Horseshoe

4. The last equation.

Hint:

Horse = 10

Cowboy-Boot = 1

HorseShoe= 2

The Last equation = 21

Detailed Explanation :

Equation1:

3Horse = 30

=> Horse = 10 .....(1)

Equation2:

1Horse + 2HorseShoe + 2HorseShoe = 18

10 + 4HorseShoe =18

HorseShoe = 2 .....(3)

Equation3:

2HorseShoe - 2Cowboy-Boot = 2

4 - 2Cowboy-Boot = 2

=> Cowboy-Boot = 1 ... (2)

Equation4:

Cowboy-Boot+Horse*HorseShoe = 1+10*2

=>21

YES NO

Cowboy-Boot = 1

HorseShoe= 2

The Last equation = 21

Detailed Explanation :

Equation1:

3Horse = 30

=> Horse = 10 .....(1)

Equation2:

1Horse + 2HorseShoe + 2HorseShoe = 18

10 + 4HorseShoe =18

HorseShoe = 2 .....(3)

Equation3:

2HorseShoe - 2Cowboy-Boot = 2

4 - 2Cowboy-Boot = 2

=> Cowboy-Boot = 1 ... (2)

Equation4:

Cowboy-Boot+Horse*HorseShoe = 1+10*2

=>21

*Did you answer this riddle correctly?*YES NO

## Joe's 10 Coins Riddle

Joe has ten coins totaling $1.19. From these coins, he cannot make exact change for a dollar, half-dollar, quarter, dime, or nickel.

What are the coins?

What are the coins?

Hint:

## Bat And Ball Riddle

If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

Hint: The answer isn't 10 cents.

Here's the solution:

Although $1.00 + $0.10 does equal $1.10, if you take $1.00 $0.10 you get $0.90, but the problem requires that the bat costs $1 more than the ball.

So, the ball must cost $0.05, and the bat must cost $1.05 since $1.05 + $0.05 = $1.10

---

Still not convinced? You can use algebra to solve the problem:

First, lets set up the equation:

x + ($1.00 + x) = $1.10

$1.00 + 2x = $1.10

2x = $1.10 $1.00

2x = $0.101

Finally, solve for x:

x = $0.05

Check your work:

x + ($1.00 + x) = $1.10, so

$0.05 + ($1.00 + $0.05) = $1.10

YES NO

Although $1.00 + $0.10 does equal $1.10, if you take $1.00 $0.10 you get $0.90, but the problem requires that the bat costs $1 more than the ball.

So, the ball must cost $0.05, and the bat must cost $1.05 since $1.05 + $0.05 = $1.10

---

Still not convinced? You can use algebra to solve the problem:

First, lets set up the equation:

x + ($1.00 + x) = $1.10

$1.00 + 2x = $1.10

2x = $1.10 $1.00

2x = $0.101

Finally, solve for x:

x = $0.05

Check your work:

x + ($1.00 + x) = $1.10, so

$0.05 + ($1.00 + $0.05) = $1.10

*Did you answer this riddle correctly?*YES NO

## At The Hardware Store Riddle

At the hardware store

I was quoted 12 cents for one,

24 cents for 50, and

36 cents for 144.

I wanted six.

What was I buying and how much did it cost me?

I was quoted 12 cents for one,

24 cents for 50, and

36 cents for 144.

I wanted six.

What was I buying and how much did it cost me?

Hint:

Prices quoted were for house numbers at 12 cents per number. A number'6' cost me 12 cents.

YES NO

*Did you answer this riddle correctly?*YES NO

## Post Your Math Brain Teasers Below

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