NCERT Class 6 Mathematics Third Chapter Playing with Numbers Exercise 3.4 Solutions

EXERCISE 3.4

(1) Find the common factors of:

(a) 20 and 28

Solution: Factors of 20 are 1, 2, 4, 5 and 10

Factors of 28 are 1, 2, 4, 7 and 14

Thus, the common factors are 1, 2 and 4.

(b) 15 and 25

Solution: Factors of 15 are 1, 3 and 5

Factors of 25 are 1 and 5

Thus, the common factors are 1 and 5.

Solution: Factors of 35 are 1, 5, and 7

Factors of 50 are 1, 2, 5, 10, and 25

Thus, the common factors are 1 and 5.

(d) 56 and 120

Solution: Factors of 56 are 1, 2, 4, 7, 8, 14 and 28

Factors of 120 are 1, 2, 3, 4, 5, 6, 8, 10, 12, 20, 24, 30, 40 and 60.

Thus, the common factors are 1, 2, 4 and 8.

(2) Find the common factors of:

(a) 4, 8 and 12

Solution: Factors of 4 are 1 and 2

Factors of 8 are 1, 2 and 4

Factors of 12 1, 2, 3, 4 and 6

Thus, the common factors are 1, 2 and 4.

(b) 5, 15 and 25

Solution: Factors of 5 is 1.

Factors of 15 are 1, 3 and 5.

Factors of 25 are 1 and 5.

Thus, the common factors are 1 and 5.

(3) Find first three common multiples of:

(a) 6 and 8

Solution: First three multiples of 6 and 8 are 24, 42 and 72

(b) 12 and 18

Solution: First three multiples of 12 and 18 are 36, 72, 108

(4) Write all the numbers less than 100 which are common multiples of 3 and 4.

Solution: 12, 24, 36, 48, 60, 72, 84 and 96.

(5) Which of the following numbers are co-prime?

(a) 18 and 35 (b) 15 and 37 (e) 216 and 215 (f) 81 and 16 are co-primes because they do not have a common factor other than 1.

(6) A number is divisible by both 5 and 12. By which other number will that number be always divisible?

Ans: 60 will be always divisible by both 5 and 12.

(7) A number is divisible by 12. By what other numbers will that number be divisible?

Ans: The numbers are 1, 2, 3, 4 and 6.