Question

Give pairs of prime numbers less than $20$ whose sum is exactly divisible by $5.$

Answer 1

As we know that prime numbers are the numbers having only two factors $1$ and itself.

Since five pairs of prime numbers, less than 20 whose sum is divisible by $5$ are $(2,3),(3,7),(2,13),(5,5),(3,17),(7,13).$

Therefore five pairs of prime numbers less than 20 whose sum is divisible by $5$ are $(2,3),(3,7),(2,13),(5,5),(3,17),(7,13).$