GMATBusters wrote:
Is the positive integer p a prime number?
(1) p is odd.
(2) 2 < p < 17
Target question: Is the positive integer p a prime number? Statement 1: p is odd. There are several values of p that satisfy statement 1. Here are two:
Case a: p = 3, in which case the answer to the target question is
YES, p is primeCase b: p = 9, in which case the answer to the target question is
NO, p is not primeSince we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: 2 < p < 17 Tip: If you feel that statement to is insufficient, see if you can RE-USE the same counter-examples be used for statement 1.
In this case, we CAN reuse those counterexamples, since they also satisfy statement 2:
Case a: p = 3, in which case the answer to the target question is
YES, p is primeCase b: p = 9, in which case the answer to the target question is
NO, p is not primeSince we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined Since I was able to use the
same counter-examples to show that each statement ALONE is not sufficient. So, the same counter-examples will satisfy the two statements COMBINED.
In other words,
Case a: p = 3, in which case the answer to the target question is
YES, p is primeCase b: p = 9, in which case the answer to the target question is
NO, p is not primeSince we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
_________________
Brent Hanneson – Creator of gmatprepnow.com
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