# 9. In which of the following expressions, prime factorisation has been done? (a) 24 = 2 $\times$ 3 $\times$ 4                    (b) 56 = 7 $\times$ 2 $\times$ 2 $\times$ 2 (c) 70 = 2 $\times$ 5 $\times$ 7                    (d) 54 = 2 $\times$ 3 $\times$ 9

P Pankaj Sanodiya

in factorization, we don't write composite numbers. All the factors should be prime numbers in this method.

(a) 24 = 2 $\times$ 3 $\times$

As we know that 4 is a composite number.
Hence This is not a prime factorization.

b) 56 = 7 $\times$ 2 $\times$ 2 $\times$ 2
In this factorization, all the factors of 56 are prime numbers. There is no composite number.
Hence This is prime factorization.

c) 70 = 2 $\times$$\times$
In this factorization, all the factors of 70 are prime numbers. There is not a composite number in this process of factorization.
Hence This is prime factorization.

d) 54 = 2 $\times$ 3 $\times$ 9
In this factorization, 54 is written as the product of 2, 3 and 9. In this factorization, 2 and 3 are prime numbers, but 9 is a composite number.
Hence This is not a prime factorization.

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