# Playing With Numbers | Class 6 Mathematics Practice Problems

Playing with numbers exercise 3.1 and 3.2 Text book solutions

Playing with numbers exercise 3.3 Textbook solutions

Given below are practice problems that students can attempt to score better.

### Playing with Numbers | Practice Problems With Answers | Class 6 NCERT Maths Solutions

1. Write the first five multiples of 50.

2. Write all the prime numbers between 1 and 20.

3. Write the numbers which are divisible by 5.

2000, 764, 2345, 9876, 755, 286

4. Check whether the number 3762 is divisible by 6. Give reasons.

5. Find the HCF of 10 and 20.

6. Which of the following numbers are co-prime?

a)18 and 35

b) 15 and 37

c) 81 and 16

7. Which of the following number is divisible by 9.

a) 2204

b) 1720

c) 3708

8. Express the following as the sum of two odd primes.

a) 26

b) 18

9. Express the following as the sum of three odd primes:

a) 31

b) 61

10. A number is divisible by 12. By what other numbers will that number be divisible?

## Answers

1. The first five multiples of 50 are 50, 100, 150, 200, and 250.

2. The prime numbers between 1 and 20 are 2, 3, 5, 7, 11, 13, 17, and 19.

3. A number which has either 0 or 5 in its ones place is divisible by 5.

Therefore, 2000, 2345 and 755 are divisible by 5.

4. If a number is divisible by 2 and 3 both then it is divisible by 6 also.

A number is divisible by 2 if it has any of the digits 0, 2, 4, 6 or 8 in its ones place.

Since 3762 is an even number, it is divisible by 2.

If the sum of the digits is a multiple of 3, then the number is divisible by 3.

Here sum of the digits = 3 + 7+ 6+ 2 = 18, which is a multiple of 3.

So it is divisible by 3.

Therefore, 3762 is divisible by 6.

5. The factors of 10 are 1, 2, 5 and 10.

The factors of 20 are 1, 2, 4,5,10 and 20.

Common factors are 1, 2, 5 and 10.

Highest Common Factor is 10.

Therefore, HCF = 10

6. Two numbers having only 1 as a common factor are called co-prime numbers.

a) The factors of 18 are 1, 2,3,6,9 and 18.

The factors of 35 are 1, 5, 7 and 35.

Common factors are 1 and 5.

So these numbers are not co-prime.

b) Factors of 15 are 1, 3, 5, and 15

Factors of 37 are 1 and 37.

Common factor is 1.

So these numbers are co-prime.

c) The factors of 81 are 1, 3, 9, 27 and 81.

Factors of 16 are 1,2,4,8 and 16.

Common factor is 1.

So these numbers are co-prime.

7. If the sum of the digits of a number is divisible by 9, then the number itself is divisible by 9.

a) Sum of the digits= 2 + 2+ 4 = 8, which is not divisible by 9.

Then the number 2204 is not divisible by 9.

b) Sum of the digits = 1 + 7+ 2+ 0 = 10, which is not divisible by 9.

Then the number 1720 is not divisible by 9.

c) Sum of the digits = 3 + 7 + 0 + 8 = 18, which is divisible by 9.

Then the number 3708 is divisible by 9.

8. 26 = 19 + 7

18 = 13 + 5

9. a) 31 = 3 + 5 + 23

b) 61 = 7 + 13 + 41

10. A number which is divisible by 12 is divisible by its factors also.

The factors of 12 are 1,2,3,4 and 6.

So the number is divisible by all these numbers.