Question

if 5 is the least Prime factor
factor of number a and 13 is the least prime factor of
number b , then the least prime factor of a + b is
​

Answer 1

Answer: 2

Step-by-step explanation: Since 5+13=18. The least prime factor of a+b has to be 2; unless a+b is a prime number greater than 2.

Suppose a+b is a prime number greater than 2. Then a+b must be an odd number. So one of a or b must be an even number. Suppose then that a is even. Then the least prime factor of a is 2; which is not 5 or 13. So a cannot be an even number. Nor can b be an even number. Hence a+b can not be a prime number greater than 2 if the least prime factor of a is 5 and b is 13.

Hence the answer is 2.