Data Sufficiency

Is n Divisible by 39?

1.N is divisible by 65
2. N is divisible by 78

My answere D
Officail answer B...why??

shilpaqueen wrote:Is n Divisible by 39?

1.N is divisible by 65
2. N is divisible by 78

My answere D
Officail answer B...why??

If N is a multiple of 39 means N is a multiple of (3*13). Thus, we need to see which contains 39 or 3 and 13 both as a factor is the options.

1. N is divisible by 65

=> N is divisible by (5 * 13)

So N may or may not be divisible by 39 as we are not sure if N contains a 3 or not. (Insufficient)

2. N is divisible by 78

=> N is divisble by (2 * 3 * 13)

So N must be divisible by 39 as we are sure N is a multiple of both 3 and 13. (Sufficient)

Moreover, 78 itself is a multiple of 39.
If something is div by 78 then bound to be div by 39.

Thus, B

N is divisible by 65

When N= 2535 ( which is equal to 65 * 39 ) .

In this case N is divisible by both 65 and 39 .


When N = 65 , N is divisible by 65 and not 39 .
Hence 1 is not sufficient ..