Q.

Find the number of factors of 120.


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a

13

b

14

c

15

d

16 

answer is D.

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Detailed Solution

120 is a type of composite number so it has more than two factors, unlike a prime number which has only two factors i.e, 1 and the number itself.
But we can express 120 in terms of its prime factors
 5 × 3 × 2 × 2 × 2 = 120
Among the 5 main factors given above, there are other factors as well.
Those other factors can be enumerated below:
Now number of factors = highest power of each prime factor multiplied by 1 highest power of other factor +1.
So, here the highest powers of 5, 3 and 2 are 1, 1 and 3 respectively.
So, 120(3+1) × (1+1) × (1+1)=16 factors.
 
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Find the number of factors of 120.