Question

If M is a prime number such that (M+1) is also prime number. What number does M(M-2) +1 represents?

Answer 1

Answer:

For 1, the only way m-n can be a prime number is if the difference = 2 because had the difference been any other prime number (which is bound to be odd), either m or n would have to be even (since E-O (or vice versa) = O. Now, if any number is even, it can be divided by 2 and hence, it cannot be a prime number (which is a required condition according to question).

if m-n = 2, mod(m-n) = 2

Hence, 1 is sufficient.

For 2, there are only 2 prime numbers less than 5 i.e. 2 and 3.

Considering this mod(m-n) can only be 1.

Hence, 2 is sufficient.

Therefore, answer is option D.