Q.9. In which of the following expressions, prime factorisation has been done?

(a) 24 = 2 × 3 × 4

(b) 56 = 7 × 2 × 2 × 2

(c) 70 = 2 × 5 × 7

(d) 54 = 2 × 3 × 9

(a) 24 = 2 × 3 × 4

(b) 56 = 7 × 2 × 2 × 2

(c) 70 = 2 × 5 × 7

(d) 54 = 2 × 3 × 9

(a) 24 = 2 x 3 x 4

Here, 4 is not a prime number.

Hence, it is not a prime factorisation.

(b) 56 = 7 x 2 x 2 x 2

Here, all factors are prime numbers

Hence, it is a prime factorisation.

(c) 70 = 2 x 5 x 7

Here, all factors are prime numbers.

Hence, it is a prime factorisation.

(d) 54 = 2 x 3 x 9

Here, 9 is not a prime number.

Hence, it is not a prime factorisation.