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GRE Math Challenge #44-prime number greater than 2
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09 Sep 2014, 03:33
09 Sep 2014, 03:33
Expert Reply
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Question Stats:
52% (00:47) correct
47% (00:43) wrong based on 17 sessions
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If n is any prime number greater than 2, which of the following CANNOT be a prime number?
A. n-4
B. n-3
C. n-1
D. n+2
E. n+5
A. n-4
B. n-3
C. n-1
D. n+2
E. n+5
Show: :: Explanation
All primes greater than 2 are odd;
So, n-4 is odd and can be prime but take n=6 gives n-4=2 is prime
n-3 could be even ie prime
n-1 sameway as above is prime
n+2 is odd and can be prime as the case is in 41, 43 & 11, 13 etc
n+5 is always even for all odds greater than 2 and hence is the answer
So, n-4 is odd and can be prime but take n=6 gives n-4=2 is prime
n-3 could be even ie prime
n-1 sameway as above is prime
n+2 is odd and can be prime as the case is in 41, 43 & 11, 13 etc
n+5 is always even for all odds greater than 2 and hence is the answer
Re: GRE Math Challenge #44-prime number greater than 2
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15 Jan 2018, 20:28
15 Jan 2018, 20:28
A? because 3-4==-1
it is less than 0? please explain, thanks
it is less than 0? please explain, thanks
Re: GRE Math Challenge #44-prime number greater than 2
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09 May 2018, 08:20
09 May 2018, 08:20
I solved the question by taking the n as 3.
as we know NEGATIVE number can not be PRIME. hence according to my N option A and B are out of choice and option C and D is prime and hence E is the answer.
as we know NEGATIVE number can not be PRIME. hence according to my N option A and B are out of choice and option C and D is prime and hence E is the answer.
