Bunuel wrote:
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.
DS20442
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 ODDSo, 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? 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 primesSince we can answer the
REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
VIDEO ON REPHRASING THE TARGET QUESTION:
_________________
Brent Hanneson – Creator of gmatprepnow.com
I’ve spent the last 20 years helping students overcome their difficulties with GMAT math, and the biggest thing I’ve learned is…
Many students fail to maximize their quant scores NOT because they lack the skills to solve certain questions but because they don’t understand what the GMAT is truly testing -
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