# 100+ Challenging math riddles to keep your mind sharp

#### 300 ft. train travelling - Math riddle

###### 1. Math Riddles
A 300 ft. train is travelling 300 ft. per minute must travel through a 300 ft. long tunnel. How long will it take the train to travel through the tunnel?

Explanation :

To calculate the time it takes for the entire 300-foot train to pass through a 300-foot long tunnel, we can use a simple mathematical approach.

Let's denote the following variables:

D (Distance of the train) = 300 feet
S (Speed of the train) = 300 feet per minute
T (Time it takes to pass through the tunnel) = ?
We can use the formula: Time (T) = Distance (D) / Speed (S).

For the front of the train to enter the tunnel until the back of the train clears the tunnel, we need to consider the entire length of the train.

The front of the train needs to travel the length of the tunnel, which is 300 feet. So, the time it takes for the front to clear the tunnel is:
T1 (Time for the front) = D / S = 300 feet / 300 feet per minute = 1 minute.

Now, as the front of the train has cleared the tunnel, the back of the train has just entered the tunnel, and it also needs to traverse the entire length of the tunnel, which is another 300 feet. So, the time it takes for the back to clear the tunnel is:
T2 (Time for the back) = D / S = 300 feet / 300 feet per minute = 1 minute.

To find the total time it takes for the entire train to pass through the tunnel, we add the time it takes for the front and the time it takes for the back:
Total Time (T) = T1 (Time for the front) + T2 (Time for the back) = 1 minute + 1 minute = 2 minutes.

Therefore, it will take a total of 2 minutes for the 300-foot train to pass through the 300-foot long tunnel.

• A.2 min
• B.3 min
• C. 4 min
• D.8 min

#### Three digit number fun - Math riddle

###### 2. Math Riddles

I am a three digit number. My second digit is four times bigger than the third digit. My first digit is three less than my second digit. Who am I?

Explanation :

Define the three-digit number: We represent the three-digit number as ABC, where A is the first digit, B is the second digit, and C is the third digit.

Define the third digit: Let the third digit C be represented by the variable x. This means C = x.

Relationship between the second and third digits: The puzzle states that the second digit is four times as big as the third digit. Therefore, we can express this relationship as:

B = 4x

Relationship between the first and second digits: The puzzle also mentions that the first digit is three less than the second digit. This relationship can be expressed as:

A = B - 3

Now, let's use these equations to find the three-digit number:

Substitute B from Equation 3 into Equation 4: We substitute the expression for B from Equation 3 into Equation 4:

A = (4x) - 3

Simplify the equation: We can simplify this expression:

A = 4x - 3

Now, we need to find values for A and x that satisfy this equation while considering the constraints of digit values (0-9).

Test values for x:

If we set x = 1, then A = 4(1) - 3 = 4 - 3 = 1. So, our three-digit number is 141.
This shows that if we choose x to be 1, the equation is satisfied, and we obtain the three-digit number 141, which fulfills all the given conditions of the puzzle. So, mathematically, "141" is a valid solution.

• A.151
• B.251
• C.131
• D.141

#### 100 pairs of dogs - Math riddle

###### 3. Math Riddles

There are 100 pairs of dogs in a zoo. Two pairs of babies are born for every dog. Unfortunately, 23 of the dogs have not survived. How many dogs would be left in total?

Explanation :

Two minutes. It takes the front of the train one minute, and the back of the train another one minute. so it will take total 2 minutes.

• A.1000
• B.900
• C.977
• D.277

#### Arrange 4 Nines Number - Math Riddle

###### 4. Math Riddles

Question: Can you arrange 4 nines to make it equal to 100 with any mathematical operation?

Explanation :

To arrange four nines (9, 9, 9, and 9) to equal 100, we can use the following equation:

99 + 9/9 = 100

99 (Two nines): We start with the number 99, which is pretty close to our target, 100.

9/9 (Nine divided by nine): Using the division operation (÷), we take one of the nines (9) and divide it by another nine (9). This operation is represented as 9/9, and it equals 1 because any number divided by itself is always 1.

Now, when we add the 99 and 1 together, we get 100:

99 + 1 = 100

So, with this arrangement and mathematical operation, we have successfully made four nines equal 100. It's a creative example of how math can surprise us with its flexibility and ingenuity.

#### Miguel And Leila Age -Math Riddle

###### 5. Math Riddles

Question: When Miguel was 6 years old, his little sister, Leila, was half his age. If Miguel is 40 years old today, how old is Leila?

Answer: She is 37 years old

Explanation :

To find Leila's current age, we can set up an equation using the information given.

Let L represent Leila's age, and M represent Miguel's age.

Given Information:

When Miguel was 6 years old, Leila was half his age. This means Leila's age was M/2 at that time.

Now Miguel is 40 years old.

Equation:

We can create an equation to represent the age relationship:

When Miguel was 6 years old, we have: M - 6 = L/2

Now that Miguel is 40 years old, we can use this equation to find Leila's age:

M - 40 = L

Solving for L (Leila's age):

L = M - 40

Given that Miguel is 40 years old:

L = 40 - 40

L = 0

So, based on the equation, Leila's age is 0, which doesn't seem accurate. However, upon reevaluating the problem, it appears there was an error in the initial response.

Revised Explanation:

The issue is that the equation initially set up is incorrect. When Miguel was 6, Leila's age was indeed half of his, which is 6/2 = 3. Now that Miguel is 40 years old, the age difference remains the same at 3 years. Therefore, Leila's current age is:

Miguel's age (40) - Age difference (3) = 37 years old.

#### Hen And Egg Cool -Math Riddle

###### 6. Math Riddles

Question - If a hen and a half lay an egg and a half in a day and a half, how many eggs will half a dozen hens lay in half a dozen days?

Explanation :

To find out how many eggs a single hen lays in one day, we can use the given information that a hen and a half lays an egg and a half in a day and a half. This can be represented as:

1.5 eggs / 1.5 days = 1 egg per day per hen

Now, let's consider the scenario where both the number of hens and the time available are increased fourfold:

Number of hens: 4 hens (4 times the original number of hens).
Time available: 6 days (4 times the original time available).
In this scenario, with each hen laying 1 egg per day, four hens will lay:

4 hens * 1 egg per day = 4 eggs per day

Over the course of 6 days, these four hens will continue to lay 4 eggs per day, resulting in a total of:

4 eggs per day * 6 days = 24 eggs

So, when both the number of hens and the amount of time available are increased fourfold, the number of eggs increases 16 times, which is mathematically represented as:

16 * 1.5 eggs = 24 eggs

• A.Two
• B.Three
• C.Four
• D.Five

#### Substract Five From 25 - Math Riddle

###### 7. Math Riddles

Question - What's the maximum number of times you can subtract five from 25?

ANSWER: Only once. This is because when you subtract five the first time, 25 becomes 20, then 15, and so on.

Explanation :

When we subtract 5 from 25, we have:

25 - 5 = 20

We can subtract 5 again:

20 - 5 = 15

We can continue:

15 - 5 = 10

And again:

10 - 5 = 5

But now, when we try to subtract 5 from 5:

5 - 5 = 0

At this point, we can't subtract 5 anymore because there is nothing left. So, you can subtract 5 only once.

This explanation clarifies that after one subtraction, 25 becomes 20, and the process continues until we reach 0, at which point we can't subtract 5 anymore. Mathematically, this is represented as:

25 - 5 = 20

20 - 5 = 15

15 - 5 = 10

10 - 5 = 5

5 - 5 = 0

This confirms that you can subtract 5 only once.

#### Leon And Turtle Aquarium - Math Riddle

###### 8. Math Riddles

Leon works at the aquarium. When he tries to put each turtle in its own tank, he has one turtle too many. But if he puts two turtles per tank, he has one tank too many. How many turtles and how many tanks does Leon have?

Answer :Leon has 3 turtles and 4 tanks.

Explanation :

1 turtle in each tank = 1 turtle too many

2 turtles in each tank = 1 tank too many

Using one of the better known heuristic to solve this question

Before that, we know that:

2 turtles in each tank = 1 tank too many

2 turtles in each tank = 2 turtles short

First, find the difference in the number of turtles in the two scenarios:

First scenario = 1 turtle too many

Second scenario = 2 turtles short

Difference in turtles = 1 - (- 2)

Difference in turtles =  3

Second, find the difference in the distribution of turtles:

First scenario = 1 turtle each tank

Second scenario = 2 turtles each tank

Difference in turtle = 2 - 1

Difference in turtles = 1

Find the number of tanks:

Number of tanks = 3 ÷ 1

Number of tanks = 3

Find the number of turtles:

Using the first scenario, there was one turtle too many

Number of tanks = 3

Number of turtles = 3 + 1

Number of turtles = 4

There are 4 turtles and 3 tanks.

#### Guess the price of shoes and hoodie -Math Riddle

###### 9. Math Riddles

The total cost of a pair of shoes and a hoodie is \$150. The hoodie cost \$100 more than the pair of shoes. How much does each item cost?

Explanation :

Let's call the cost of the pair of shoes "x".

Since the hoodie costs \$100 more than the pair of shoes, its cost is x + \$100.

The total cost of the pair of shoes and the hoodie is \$150, so:

x + (x + \$100) = \$150
2x + \$100 = \$150
2x = \$150 - \$100
2x = \$50
x  = \$50/2
x = \$25

So, the pair of shoes cost \$25, and the hoodie costs \$125 (\$25 + \$100).

#### Eight Four Together Equation - Maths Riddle

###### 10. Math Riddles

How can you add eight fours together so the total adds up to 500?

Explanation :

The equation you provided is:

444 + 44 + 4 + 4 + 4 = 500

Here's the breakdown of this equation in a mathematical manner:

Add the first two numbers: 444 + 44 = 488
Add 4 to the result: 488 + 4 = 492
Add another 4: 492 + 4 = 496
Finally, add the last 4: 496 + 4 = 500
So, by following these mathematical operations step by step, you can indeed arrive at the result of 500. The equation shows that by combining these numbers and using addition, you can make 444 + 44 + 4 + 4 + 4 equal 500.

#### Men And Tables Count -Math Riddle

###### 11. Math Riddles

If 4 men can build 4 tables in 4 hours, how many tables can 8 men build in 8 hours?

Explanation :

Given information:

16 tables
4 men
4 hours
4 tables
We want to find out how many tables can be built by a certain number of men working for a specific amount of time.

First, we establish the rate at which a single man can build a table in 4 hours:

4 men in 4 hours can build 4 tables.
So, 1 man can build 1 table in 4 hours.
Next, we determine the rate of table production for a single man in 8 hours (double the time):

If 1 man makes 1 table in 4 hours, he will make 1/4 of a table in 1 hour.
In 8 hours (double the time), 1 man will make (1/4) * 8 = 2 tables.
To find how many tables 8 men can build in 8 hours, we multiply the rate of production per man by the number of men:

8 men working together will make 8 * 2 = 16 tables in 8 hours.

#### Three brothers sacks - Math Riddle

###### 12. Math Riddles

Three brothers live in a farm. They agreed to buy new seeds: Adam and Ben would go and Charlie stayed to protect fields. Ben bought 75 sacks of wheat in the market whereas Adam bought 45 sacks.At home they split the sacks equally. Charlie had paid 1400 dollars for the wheat.

How much dollars did Ben and Adam get of the sum considering equal split of the sacks?

Explanation :

Total sack bought = 45 + 75 = 120 sacks
Every farmer's part is 1/3 (45+75)
Each get = 120/3 = 40 Sacks
Charlie paid \$1400 for 40 sacks.
Amount of 1 sack = 1400/40 = 35 \$

Adam got money for 45 - 40 = 5 sacks
Adam got = 5 * \$35(per sack amount) = 175 \$

Ben bought = 75 sacks
Ben got money for 75 - 40 = 35 sacks
Ben got = 35 * \$35 = \$ 1225

Ben got = \$ 1225

#### Grand Father, Father and Son - Math Riddle

###### 14. Math Riddles

A grandfather, two fathers, and two sons went to the movie theater together, and everyone bought one movie ticket each. How many tickets did they buy in total?

Explanation :

Let's denote:

G = Grandfather F = Father S = Son

According to the information given:

1. The Grandfather is also a Father (G = F)
2. The Father is also a Son (F = S)

This can be represented using the following equations:

1. G = F
2. F = S

Now, let's consider the scenario at the movie theater:

1. The Grandfather (G) bought 1 ticket.
2. The Father (F) bought 1 ticket.
3. The Son (S) bought 1 ticket.

So, the total number of tickets bought can be represented as:

G (tickets) + F (tickets) + S (tickets)

Substituting the relationships from above:

1 ticket (G) + 1 ticket (F) + 1 ticket (S)

Since G = F and F = S, we can substitute to simplify:

1 ticket (G) + 1 ticket (G) + 1 ticket (G)

Combining like terms:

3 tickets (G)

Therefore, the total number of tickets they bought is 3, which confirms the original answer.

#### How Many Ducks ? -Math Riddle

###### 15. Math Riddles

There are two ducks in front of two other ducks. And, there are two ducks behind two other ducks. There are two ducks beside two other ducks. How many ducks are there?

Explanation :

I apologize for the confusion in my previous responses. Let's provide a mathematical explanation for the correct answer:

In this case, the riddle is referring to an arrangement of ducks where there are four ducks forming a square. So, mathematically, you can represent it as follows:

D1 - D2
| |
D3 - D4

Here, each 'D' represents a duck, and they are arranged in a square with four ducks: D1, D2, D3, and D4.

So, the correct answer is indeed four ducks forming the square.

Mathematically, we can represent it as:

Number of ducks in the square = 4 (D1, D2, D3, D4)

Therefore, there are four ducks in total, arranged in a square as described in the riddle.