Does positive integer a equal 5? (1) a is a not factor of 6

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by Brent@GMATPrepNow » Sun Sep 15, 2019 5:08 am

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BTGmoderatorDC wrote:Does positive integer a equal 5?

(1) a is a not factor of 6006.
(2) 5 is the largest divisor of a.
Target question: Does positive integer a equal 5?

Statement 1: a is a not factor of 6006.
There are several values of a that satisfy statement 1. Here are two:
Case a: 5 is not a factor of 6006, so, it could be the case that a = 5. In this case, the answer to the target question is YES, a = 5
Case b: 4 is not a factor of 6006, so, it could be the case that a = 4. In this case, the answer to the target question is NO, a does NOT equal 5
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: 5 is the largest divisor of a.
Key concept: If N is a positive integer, then then the greatest divisor of N is N.
So, statement 2 is telling us that a = 5, in which case, the answer to the target question is YES, a = 5
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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