35 Mathematical Riddles with Answers

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

Try to solve the Riddle shown in the images below:

Explanation to Image 1-

• So there are 4 Computer and cost is 40
  Computer + Computer + Computer + Computer = 40 (if 4 Computers cost is 40 so 1 Computer → 10)

• Mouse + Mouse + Mouse + 10 = 16 {Computer = 10}
  So, 3 Mouse = 6
  1 Mouse = 2

• Keybaord + 10 + Keybaord + 2 = 18 {Mouse = 2}
  So, 2 Keybaord = 6
  1 Keybaord = 3

• Now we just add all values: {Computer = 10, Mouse = 2, and Keyboard = 3}
  Computer + Keybaord + Mouse + Mouse
  10 + 3 + 2 + 2 = 17

Explanation to Image 2 -

• Number around First Circle - 7, 4. 6, 8
  Now add them all = 7 + 4 + 6 + 8 = 25
  So the center number is 25.

• Number around Third Circle = 11, 6, 3, 9
  Add them :
  11 + 6 + 3 + 9 = 29
  So the center number is 29.

• Number around the Center Circle = 5, 10, 1, 2
  Add them : 5 + 10 +1 + 2 = 18
  So the missing value is 18.

Similarly, try to solve these 35 questions; answers with explanations are given at the end.

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

Question 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?

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

Question 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 to the picnic?

Question 5: What number do you get when you multiply all the numbers on a telephone dial pad?

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

Question 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 there be in total?

Question 8: What is 7 + 7 ÷ 7 + 7 x 7 - 7 ?

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

Question 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]

Question 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?

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

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

Question 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?

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

Question 16: I am a number, but when you add 'G' to me, I go away. What number am I?

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

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

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

Question 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?

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

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

Question 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?

Question 24: What three positive numbers, after addition and multiplication, give the same result?

Question 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?

Question 26: The total cost of a pen and a notebook is ₹150. The pen costs ₹100 more than the notebook. How much does each item cost?

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

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

Question 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?

Question 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?

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

Question 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?

Question 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.

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

Question 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:

Answer 1: Add "x" between ninety and eight [Ninety x Eight = 720].

Answer 2: 11 Cartons

Explanation: 56 + 40 = 96

• Large Boxes: 7 [7 x 8 = 56]
• Small Boxes: 4 [4 x 10 = 40]

Answer 3: 888 + 88 + 8 + 8 + 8 = 1,000.

Answer 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 = 13

• Couple: 2 people
• Sons: 5
• Sisters: 3
• Babies: 3

Answer 5: Zero (0)

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

Answer 6: 21

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

Answer 7: 21

Explanation: 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.

6 + 5 + 4 + 3 + 2 + 1 = 21

Answer 8: 50

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

1. 7 ÷ 7 = 1
   7 + 1 + 7 x 7 - 7
2. 7 x 7 = 49
   7 + 1 + 49 - 7
3. 8 + 49 = 57
   57 - 7
4. 57 - 7 = 50

Answer 9: 3 apples because you took away three apples

Answer 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

Answer 11: 141.

Answer 12: Once

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

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

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

Answer 15: 31

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

Answer 16: One

Explanation: After adding G to one, it becomes GONE.

Answer 17: Decimal

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

Answer 18: Number 8

Answer 19: My Age = 40, Daughter's Age = 10

Explanation: Let's assume the daughter's age be x,
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

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

Answer 21: 99 students

Answer 22: 0

Answer 23: 72 cm

Explanation: The size of the bird's head is 9 cm.
Tail = 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 cm

Tail = 9 + 1/2(36)
Tail = 27 cm

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

Answer 24: 1, 2, and 3

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

Answer 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

Answer 26: Cost of Pen = ₹100, Cost of Notebook = ₹25

Answer 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 = x2  2x​  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 = x2  2x​  + 50, Father's age = 2x + 50

According to the question,
x/2 + 50 = Half of (2x + 50)
x = Raj's Age = 50 years

Answer 28: 6457

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

Answer 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 need d of the four-minute timer)

Answer 30: 14 horses and 8 men

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

Answer 31: 55 + 5 = 60

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

Answer 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 = d44d​
b = 6d4=32d46d​=23​d
c = 32d+323​d+3

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.

Answer 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

Answer 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 glance, 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 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.

Also, Check these Challenging Puzzles: [ Mathematical Puzzle ]