# 100+ Challenging math riddles to keep your mind sharp

#### Find The Missing Number - Math Riddle

###### 76. Math Riddles

Can you find the missing number?

2

Explanation :

The answer will be 2. Look at how many closed areas there are.
9999 has 4 closed areas (the top of the '9').
8888 has 8 closed areas (the top and bottom parts of 8 and there are no other digits).
1816 has 3 closed areas (top and bottom of 8 and bottom of 6, and it has 2 other digits (3 * 2 = 6)).
1212 has 0 closed areas, (0 * 4 = 0),
Therefore,
1919 has 2 closed areas. (the top of the '9').

#### Missing Number - Math Riddle

###### 77. Math Riddles

Can you find the missing number?

Explanation :

The number that should replace the question mark is 9.
Why?
The sum of the three numbers on each die equals the number written below it.
For the first die, for example: 8 + 4 + 7 = 19;
for the second: 8 + 2 + 1 = 11.
Following this pattern would explain why the third die is also 11 (5 + 5 + 1)
and why the mysterious question mark should be 9 (4 + 3 + 2).

#### Chess Board - Math Riddle

###### 78. Math Riddles

How many squares are there in a chessboard?

Explanation :

1, 8x8 square
4, 7x7 squares
9, 6x6 squares
16, 5x5 squares
25, 4x4 squares
36, 3x3 squares
49, 2x2 squares
64, 1x1 squares
Therefore, there are actually 64 + 49 + 36 + 25 + 16 + 9 + 4 + 1 squares on a chessboard! (in total 204).

#### Rita studies for 2 hours - Math Riddle

###### 79. Math Riddles

It is 9 am now. Rita studies for 2 hours, takes a bath for 1 hour, and then has lunch for 1 hour. How many hours are left before 9 am tomorrow?

Explanation :

There will be 24 hours between 9 am today and 9 pm tomorrow.

Assumption- All the activities are performed consecutively without break

Hours consumed = 2+1+1 = 4 hours

Therefore hours remaining = 24 — 4 = 20 hours before 9 am tomorrow

#### If it is two hours later - Math Riddle

###### 80. Math Riddles

If it is two hours later, then it will take half as much time till it's midnight as it would be if it were an hour later. What time is it?

Explanation :

9 pm, or 21.00 if you prefer military time.

If it were two hours later, it would be 11 pm (23.00) — and one hour to midnight.

If it were one hour later, it would be 10 pm (22.00) — and two hours to midnight.

So, if it were two hours later than it currently is, it would take half as much time to reach midnight as it would if it were one hour later. It’s 9 pm.

#### A duck was given \$9 - Math Riddle

###### 82. Math Riddles

A duck was given \$9, a spider was given \$36, and a bee was given \$27. Based on this information, how much money would be given to a cat?

Explanation :

Assuming there’s a mathematical order to this (not a troll question) the things that stand out would be that all the numbers are divisible by 3 and 9, and the main difference between ducks, spiders, bees, and cats would be the number of legs.

From there we have the following

Duck (2 legs): 3 * 3 = 9 * 1

Bee (6 legs): 3 * 9 = 9 * 3

Spider (8 legs): 3 * 12 = 9 * 4

It’s now easy to see. Therefore, if n = pairs of legs, then the amount of money each animals receives is 9n. A cat with 2 pairs of legs would receive 2 * 9 = \$18

#### Speed of a train is 3 m/s - Math Riddle

###### 83. Math Riddles

The speed of a train is 3 meters/second and it takes 10 seconds to cross a lamp post. What is the length of the train?

Explanation :

A 30 meters. The time taken by the train to pass the stationary object is equal to the length of the train divided by the speed of the train.

#### Equation photo- Math Riddle

###### 87. Math Riddles

Can you solve this?

Explanation :

You see, sometimes it's necessary to compare apples and bananas. Or, in this case,
it could be pears instead of bananas.
Pear = 9, apple = 6, plum = 4 and these make the answers 7 and 1 respectively.
so 4+9+6 =19.ers 7 and 1 respectively.

#### Watermelon Photo- Math Riddle

###### 89. Math Riddles

Can you find the missing number?

Explanation :

You can see that the red slice of the watermelon is 2, the yellow slice is 3 and the blue one is 1. So, the answer is?5!