BTGModeratorVI wrote: ↑Sat Feb 15, 2020 2:42 pm
Is n an integer greater than 14?
(1) 3n is a positive integer.
(2) n/3 is a positive integer.
Source: Official Guide
Answer:
E
Target question: Is n an integer greater than 14?
Statement 1: [m]3n[/m] is a positive integer.
There are several values of n that satisfy statement 1. Here are two:
Case a: n = 15. In this case, the answer to the target question is
YES, n is greater than 14
Case b: n = 3. In this case, the answer to the target question is
NO, n is not greater than 14
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: [m][fraction]n/3[/fraction][/m] is a positive integer.
Important: Notice the SAME n-values that's satisfied statement 1 also satisfy statement 2. So let's reuse them.
Case a: n = 15. In this case, the answer to the target question is
YES, n is greater than 14
Case b: n = 3. In this case, the answer to the target question is
NO, n is not greater than 14
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Since we were able to use the
same counter-examples to show that statements 1 and 2
alone are insufficient, the same counter-examples can be used to show that the
combined statements are insufficient
That is...
Case a: n = 15. In this case, the answer to the target question is
YES, n is greater than 14
Case b: n = 3. In this case, the answer to the target question is
NO, n is not greater than 14
Since we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
