Question

if x is the smallest prime number greater than 21 and y is the largest prime number less than 16,then xy is equal to :

Answer 1

Step-by-step explanation:

The next prime above 21 is 23, since 22 is even. So a is 23.

The greatest prime less than 16 is 13, so b is 13.

Rather than multiply 13 and 23, notice that if you did, the units digit of the number will be 9, since 3x3 is 9. Since A is the only answer ending in 9