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Thread: Easy data sufficiency question that's confusing. OG 12th ed

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    Easy data sufficiency question that's confusing. OG 12th ed

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    Is X an integer?
    1. X/2 is an integer
    2.2x is an integer.

    The answer is A.

    I'm confused because the book states that according to 1, X would be an even integer and so that should make it sufficient. But why would that be true if when X=1, X/2=1/2? Or am I approaching it the wrong way?

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    izzai:

    you are reading it the wrong way.
    1. says X/2 is an integer that means X/2 = 1 or 2 or 3 etc. so X =2,4,6 etc. You can't assume X=1 because, they say X/2 is an integer which means X is even.

    Let me know if this helps

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    It does! Thank you!

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    Answer

    Agree with a

    Put in x= 1,1/2,3/2,2, only first statement satisfies

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    yes it is important to make sure that you are clear about what the question is asking. Here (1) says that x divided by two is an integer, this means that x has to be an integer because it must be an even integer to mean that x/2 is an integer. (2) says that x multiplied by 2 is an integer that means that x could be an integer, like 1 or that it could not be like 1/2
    Last edited by BGPC Eliza; 11-21-2014 at 10:09 AM.
    Eliza Chute, GMAT Tutor
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    Quote Originally Posted by izzai View Post
    Is x an integer?
    1) x/2 is an integer
    2) 2x is an integer.
    Target question:Is x an integer?

    Statement 1: x/2 is an integer
    In other words, x/2 = k, where k is an integer
    Multiply both sides by 2 to get: x = 2k
    In other words, x = (2)(some integer k)
    If k is an integer, then
    x is an integer (an EVEN integer at that)
    Since we can answer the target question with certainty, statement 1 is SUFFICIENT

    Statement 2: 2x is an integer
    There are several values of x that satisfy this condition. Here are two conflicting cases:
    Case a: x = 1, in which case 2x = 2(1) = 2, and 2 is an integer. In this case, x IS an integer
    Case b: x = 1.5, in which case 2x = 2(1.5) = 3, and 3 is an integer. In this case, x is NOT an integer
    Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

    Answer = A

    Cheers,
    Brent

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