Question

Let $pq$ be a two-digit prime number less than $20$. If after reversing the digits, $qp$ is also a prime, then $p+q$ can be

• A. $2$
• B. $4$
• C. $8$
• D. $10$

Answer 1

Answer: (A), (B), (C)

The correct options are
A $2$
B $4$
C $8$

Two-digit primes less than $20$ are
$pq=11,13,17,19$
Then, $qp=11,31,71,91$
But $91=13\times 7$ is not a prime.
Hence, $p+q$ can be $1+1,3+1,7+1$,
i.e., $p+q=2,4,8$