Hi All,

This question can be solved by TESTing VALUES, although you'll have to do a little bit of extra work at the end to prove that your answer is correct.

We're told that X is a POSITIVE INTEGER. We're asked if (X-1)(X+1) is divisible by 24. This is a YES/NO question.

Fact 1: X is NOT divisible by 3.

IF...

X = 1

(0)(2) = 0 and the answer to the question is YES.

X = 2

(1)(3) = 3 and the answer to the question is NO.

Fact 1 is INSUFFICIENT

Fact 2: X-1 is divisible by 2

This means that X MUST be ODD.

IF...

X = 1, then the answer to the question is YES (we did the work in Fact 1 already).

X = 3

(2)(4) = 8 and the answer to the question is NO

Fact 2 is INSUFFICIENT

Combined, we know...

X MUST be odd

X is NOT divisible by 3

IF....

X = 1, then the answer to the question is YES

X = 5

(4)(6) = 24 and the answer to the question is YES

X = 7

(6)(8) = 48 and the answer to the question is YES

X = 11

(10)(12) = 120 and the answer to the question is YES

We have a consistent result.

Combined, SUFFICIENT

Final Answer:

GMAT assassins aren't born, they're made,

Rich

_________________

Official Guide 2016 Question Breakdown:

http://gmatclub.com/forum/empowergmat-blog-198415.html#p1527977

Rich Cohen

Rich.C@empowergmat.com

http://www.empowergmat.com

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