BTGModeratorVI wrote: ↑Fri May 29, 2020 6:26 am
Is the sum of four different positive prime integers an odd integer?
(1) One of the integers is 11.
(2) One of the integers is 2.
Answer:
B
Source: GMAT prep
Target question: Is the sum of four different positive prime integers an odd integer?
This is a good candidate for
rephrasing the target question.
The key concept involved here is that 2 is the only EVEN prime number, and all other prime numbers are ODD
So, if 2 is among the four primes, then the sum =
EVEN +
ODD +
ODD +
ODD = ODD
If 2 is NOT among the four primes, then the sum =
ODD +
ODD +
ODD +
ODD = EVEN
So, in order for the sum to be ODD, 2 must be among the four primes.
This means we can rephrase the target question as follows:
REPHRASED target question: Is 2 among the four primes?
Aside: Here’s a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Statement 1: One of the integers is 11.
Since we have no information about the other three primes, 2 may or may not be among them.
Since we cannot answer the
REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: One of the integers is 2.
Perfect!
The answer to the REPHRASED target question is
YES, 2 is among the four primes
Since we can answer the
REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
