Question

A and b are two positive integers such that least prime factor of a is 3 and b is 5 . Find the least prime factor of (a+b).
I think a+b will be even no. as a is odd and b is odd,this odd +odd =even
Least prime factor of a even no is 2.
Ans is 2

Answer 1

Least prime factor being 3 or 5 means that 2 is not a factor. So the numbers are both odd.

Odd + odd = even for sure. So for a+b we have 2 as a prime factor.


Since 2 is the smallest prime, answer is 2.

Answer 2

5+3=8
8 factors are 2,2,2
therefore 2 is the factor of (a+b)