Bunuel
Is 6x/13 an integer?
(1) x is a prime number
(2) 3x is divisible by 13
Target question: Is 6x/13 an integer?ASIDE: In order for 6x/13 to be an integer, 6x must be divisible by 13. Statement 1: x is a prime number Let's TEST some values.
There are several values of x that satisfy statement 1. Here are two:
Case a: x = 13. In this case, 6x/13 = 6(13)/13 = 6. So, the answer to the target question is
YES, 6x/13 IS an integerCase b: x = 2. In this case, 6x/13 = 6(2)/13 = 12/13. So, the answer to the target question is
NO, 6x/13 is NOT an integerSince we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: 3x is divisible by 13If 3x is divisible by 13, then we can say that
3x = 13k for some integer k.
Notice that: 6x/13 = (2)(
3x)/13
Replace values to get: 6x/13 = (2)(
3x)/13 = (2)(
13k)/13 = 2k = some integer
[if k is an integer, then 2k must also be an integer]So, the answer to the target question is
YES, 6x/13 IS an integerSince we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent