Question

a and b are two positive integers such that the least prime factor of a is 3 and the least prime factor of b is 5. Then, the least prime factor of (a + b) is ______.

Options

• 2

• 3

• 5

• 8

Answer 1

a and b are two positive integers such that the least prime factor of a is 3 and the least prime factor of b is 5. Then, the least prime factor of (a + b) is 2.

Explanation:

Clearly, 2 is neither a factor of a nor that of b.

∴ a and b are both odd.

Hence, (a + b) is even.

∴ Least prime factor of (a + b) is 2.