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
(a) 2
(b) 3
(c) s
(d) 8
​

Answer 1

Given that:-

• a is a positive integer and 3 is least prime factor of a.
• Also, b is a positive integer and 5 is least prime factor of b.

Solution:-

•Since least prime factor of a is 3, it implies that 'a' is an odd number

∴ if a is even then 2 is least prime factor of a.

•Similarly b is also an odd number.

Now, it is known that sum of two odd numbers is an even number.

Hence

• a + b will be an even number.

∴ The least prime factor of a + b is 2.