Question

A= 13+26+39+...+169

What is the sum of the prime numbers that can divide A ?


A)16 B)18 C)20 D)22 E)24

Answer 1

A= 13+26+39+...+169=

= 13(1+2+3+....+13)=

=13* (13*14)/2=

=13*13*7

=> 13+7=20

So the answer is c)