Question

The least prime factor of $a$ is $3$ and least prime factor of $b$ is $7$, then what is least prime factor of $(a+b)$

Answer 1

Since, 3 is the least prime factor of 'a' therefore the number 'a' must be odd (because if the numbers would have been even then the least prime factor will definitely be 'z'.)

So, a is odd. similarly, b is also odd.

Hence a+b is even (than is, a multiple of 2)

Thus the least prime factor of 'a+b' is 2.