# In which of the following expressions, prime factorization has been done?

(a) 24 = 2 × 3 × 4

(b) 56 = 7 × 2 × 2 × 2

(c) 70 = 2 × 5 × 7

(d) 54 = 2 × 3 × 9

**Solution:**

We will use the concept of prime factorization to solve this.

(a) 24 = 2 × 3 × 4

Here, 4 is not a prime number in the given factorization of 24.

Thus, 24 = 2 × 3 × 4 is not the correct way of prime factorization.

(b) 56 = 7 × 2 × 2 × 2

Here, in the factorization of 56, all factors are prime numbers

Hence, 56 = 7 × 2 × 2 × 2 is the correct way of prime factorization.

(c) 70 = 2 × 5 × 7

Here, in the factorization of 70, all factors are prime numbers.

Hence, 70 = 2 × 5 × 7 is a correct way of prime factorization.

(d) 54 = 2 × 3 × 9

Here, 9 is not a prime number in the given factorization of 54.

Hence, 54 = 2 × 3 × 9 is not a correct way of prime factorization.

You can also use the prime factorization calculator to solve this,

NCERT Solutions Class 6 Maths Chapter 3 Exercise 3.5 Question 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

**Summary:**

In options (b) 56 = 7 × 2 × 2 × 2 and (c) 70 = 2 × 5 × 7, prime factorization has been done.