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\times 7                    (d) 54 = 2 \times 3 \times 9

Answers (1)
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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