# 35 Mathematical Riddles with Answers

A mathematical riddle is a remark or question phrased purposefully and requires creativity to determine the meaning or answer. Basically, these riddles are more like logical problems which require knowledge of mathematics to solve them.

Here are some Mathematical Riddles with their answers at the end.

## Mathematical Riddles

1. How do you go from 98 to 720 using just one letter?

2. A merchant can place 8 large boxes or 10 small boxes into a carton for shipping. In one shipment, he sent a total of 96 boxes. How many cartons did he ship if there are more large boxes than small boxes?

3. Can you write down eight eights so that they add up to one thousand?

4. A couple went for a picnic. They have 5 sons and each son has three sisters. Each sister has one baby. In total how many people went for the picnic?

5. What number do you get when you multiply all the numbers of a telephone dialpad?

6. What is the next number in the sequence 2, 3, 5, 8, 13?

7. There are seven people at a party. They meet each other and each of them shakes hands only once with each of the others. How many handshakes will be there in total?

8. What is 7 + 7 Ã· 7 + 7 x 7 – 7 ?

9. If there are four apples and you take away three of them, how many apples do you have?

10. A father and his son’s ages add up to 66. The father’s age is the reverse of his son’s age. How old are they?

[** Note: **There are 3 possible answers]

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

12. How many times can you subtract five from twenty-five?

13. I add five to nine and get two as the answer. The answer is accurate. How?

14. Two fathers and two sons went fishing one day. At the end of the day, each of them had one fish. There were three fish in total. How is it possible?

15. If 7 is transformed into 13 and 11 into 21, what does 16 become?

16. I am a number, but when you add ‘G’ to me, I go away. What number am I?

17. What can you put between 7 and 8 to get a result bigger than 7, but not quite as high as 8?

18. Turn me on my side and I am everything. Cut me in half and I am nothing. What am I?

19. I am four times as old as my daughter. 20 years from now, I will be twice as old as her. How old are we now?

20. You are running a race with a group of people and pass the person in second place. What place would you be in now?

21. If Reema is the 50^{th} fastest and 50^{th} slowest runner in her school. How many students are there in the school?

22. Three times what number is not larger than two times the same number?

23. The head of a bird is 9 cm long. Its tail is equal to the size of its head plus half the size of its body. Also, its body is equal to the size of its head plus its tail. The length of the bird will be?

24. What three positive numbers after addition and multiplication give the same result?

25. A zoo has 100 pairs of dogs. Every dog gave birth to two pairs of babies. Unfortunately, 23 of the dogs did not survive. How many dogs are left in the zoo in total?

26. The total cost of a pen and a notebook is â‚¹150. The pen cost â‚¹100 more than the notebook. How much does each item cost?

27. Raj is twice as old as his little sister and half as old as his father. After 50 years from now, his sister will be half their father’s age. What is Raj’s age now?

28. Find the next number in the series 7645, 5764, 4576, ……….

29. You want to boil an egg for two minutes. If there is only a three-minute timer, a four-minute timer, and a five-minute timer, how can you boil the egg for two minutes only?

30. There are men and horses in a stable. In total, there are 22 heads and 72 feet. How many men and horses are there in the stable?

31. 20 + 20 + 20 = 60. Make it 60 again by using a number three times (it can’t be 20).

32. You are 8 feet away from a door and with each move you take, you cover half the distance to the door. How many moves will it take to reach the door?

33. What is the four-digit number in which the first digit is one-fourth of the last digit? The second digit is 6 times the first digit, and the third digit is the second digit plus 3.

34. How can you get 720 by using six zeros and any mathematical operator?

35. Abir has a box of ornaments that he uses to decorate his tree on Christmas each year. All of them are blue (except for six), all of them are green (except for six), and all of them are red (except for six). How many ornaments are there of each colour?

## Answers:

** 1.** Add “x” between ninety and eight [Ninety x Eight = 720]

**2. 11 Cartons**

Explanation:Large Boxes: 7 [7 x 8 = 56]

Small Boxes: 4 [4 x 10 = 40]

56 + 40 = 96

** 3.** 888 + 88 + 8 + 8 + 8 = 1,000

** 4.** A couple has 5 sons and each son has three sisters, which means that the couple has three daughters. Now each daughter has a baby; meaning, there are three babies in the family.

Explanation:

Total Members = 13Couple: 2 people

Sons: 5

Sisters: 3

Babies: 3

**5. Zero (0)**

As one of the numbers on a telephone’s dial pad is 0, the product of all numbers will be zero.Explanation:

**6. 21**

2 + 3 = 5; 3 + 5 = 8; 5 + 8 = 13; 8 + 13 = 21Explanation:

**7. 21**

There are 7 people in total. It means the first person will shake hands with the rest of the 6 people. Now the next person in line will shake hands with the remaining 5 people (as he has already shaken hands with the first person). Similarly, the third person will shake hands with 4 people, the fourth person will shake hands with 3 people, the fifth person with 2 people, and the sixth person will shake hands with the remaining one person.Explanation:6 + 5 + 4 + 3 + 2 + 1 = 21

**8. 50**

We will apply BODMAS (Bracket Off Divide Multiply Addition Subtraction) rule:Explanation:

- 7 Ã· 7 = 1

7 + 1 + 7 x 7 – 7- 7 x 7 = 49

7 + 1 + 49 – 7- 8 + 49 = 57

57 – 7- 57 – 7 = 50

** 9. 3 apples** because you took away three apples

** 10. **First Case: Father’s age = 51, Son’s age = 15

Second Case: Father’s age = 42, Son’s age = 24

Third Case: Father’s age = 60, Son’s age = 06

**11. 141**

**12. Once**

It is because once you subtract 5 from 25, you get 20 as the answer. Now you no longer have 25.Explanation:

** 13. **When it is 9 a.m. and we add 5 fours to it, we get 2 p.m.

** 14. **It is because there were only three people: Grandfather, Father, and Son.

**15. 31**

7 x 2 – 1 = 13; 11 x 2 – 1 = 21; 16 x 2 – 1 = 31Explanation:

**16. One**

After adding G to one, it becomes GONE.

**17. Decimal**

7.8 is bigger than 7 but not quite as high as 8.

**18. Number 8**

** 19. **My Age =

**Daughter’s Age =**

**40,**

**10**

Let’s assume the daughter’s age be x,Explanation:My age = 4x

20 Years from now, my daughter’s age will be x + 20 and my age will be 4x + 20. Also, my age is twice her age, therefore,

2(x + 20) = 4x + 20

2x + 40 = 4x + 20

x = 10.

Daughter’s Age = 10 years, My Age = 4x = 40 years

** 20. Second Place, **because you passed the person running in second place.

**21. 99 students**

**22. 0**

**23. 72 cm**

The size of the bird’s head isExplanation:.9 cmTail = 9 + Half of the size of the Body

Body = 9 + Tail size

Body = 9 + 9 + 1/2(Body)

Body – 1/2(Body) = 18

Body = 36 cmTail = 9 + 1/2(36)

Tail = 27 cm

Total length of the Bird = 9 + 36 + 27 = 72 cm

**24. 1, 2 and 3**

Explanation:1 + 2 + 3 = 6 and 1 x 2 x 3 = 6

**25. 977 dogs**

Explanation:100 pair of dogs = 100 x 2 = 200 dogs

Two pairs of babies to each dog (200 dogs) = 200 x 4 = 800 dogs

23 dogs did not survive

Total dogs left = 200 + 800 – 23 = 977 dogs

**26. Cost of Pen = â‚¹100, Cost of Notebook = â‚¹25**

**27. 50 years**

Explanation:Let’s assume Raj’s age be x years. Raj is twice as old as his sister, which means that his sister is half of Raj’s age. Thus,

Sister’s Age = years

Also, Raj is half his father’s age, which means that his father is twice the age of Raj. Thus,

Father’s Age = 2x years

50 years from now,

Raj’s sister’s age = + 50, Father’s age = 2x + 50

According to the question,

x/2 + 50 = Half of (2x + 50)

x = Raj’s Age = 50 years

**28. 6457**

The last number is moved to the front to make the next new numberExplanation:

** 29. **Start the three-minute timer and five-minute timer simultaneously. When the three-minute timer ends start boiling the egg and take it out of the water when the five-minute timer has ended. This way the egg is boiled for two minutes only. (There is no neea d of four-minute timer)

** 30. **14 horses and 8 men

14 + 8 = 22 headsExplanation:(14 x 4) + (8 x 2) = 56 + 16 = 72 feet

**31. 55 + 5 = 60**

** 32. Infinite, **because you will always reach half the distance to the door, no matter how small distance you move.

**33. 1694**

Explanation:Let the first four digits be a, b, c, and d.

According to the question, a = d/4, b = 6a, and c = b + 3

Convert each equation in terms of d. So,

a =

b =

c =

Now, use the hit and trial method to find the value of d from 0 to 9. If we take values 0 to 3 for d, a would be either 0 or a fraction. So, let’s take d = 4, then

a = 1, b = 6, and c = 9

All these satisfy the conditions given. Therefore, the four-digit number will be 1694.

**34. (0! + 0! + 0! + 0! + 0! + 0!)!**

Explanation:(1 + 1 + 1 + 1 + 1 + 1)! = 6!

6! = 6 x 5 x 4 x 3 x 2 x 1 = 720

**35. 3 Blue, 3 Green, and 3 Red**

### Benefits of Mathematical Riddles

- Math riddles help in developing our analytical skills in many ways. At first look, a puzzle may look weird or absurd, but it forces us to use our analytical and critical thinking in different ways to solve the problem.
- Mathematical riddles also help in enhancing concentration and comprehension. While solving a riddle, the ability required to decipher the text is not the same as deciphering a simple sentence. Riddles require reading between the lines, thinking about the given context, and comprehending the different layers of meaning. Thus, solving riddles can increase the concentration power of a student.
- Mathematical riddles increase vocabulary. Through riddles, students can learn a variety of new and odd words including homophones and metaphors.
- Mathematical riddles are also good for a student’s mental health. It can boost a child’s mood and make them laugh. It can also reduce stress and give children a sense of accomplishment.