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factor problem

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jamesk486 Really wants to Beat The GMAT! Default Avatar
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factor problem Post Wed Apr 11, 2007 2:16 am
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  • Lap #[LAPCOUNT] ([LAPTIME])
    X is a prime and y is a positive integer, How many different factors of (2^3)*(x^y) are there?
    (1) x=5
    (2) y=3

    I got stuck in the middle, after figuring out that the number of factors would be (3+1)(y+1)...but someone told me that x could not be 2 or something like that..anyways i'm pretty lost!

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    ajith GMAT Titan
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    Post Thu Apr 12, 2007 2:51 am
    jamesk486 wrote:
    X is a prime and y is a positive integer, How many different factors of (2^3)*(x^y) are there?
    (1) x=5
    (2) y=3

    I got stuck in the middle, after figuring out that the number of factors would be (3+1)(y+1)...but someone told me that x could not be 2 or something like that..anyways i'm pretty lost!
    If 2 is a factor of x the number of factors of (2^3)*(x^y) would not be (3+1)(y+1)

    So we need to know x as well as y to determine the number of factors.

    Smile

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    jamesk486 Really wants to Beat The GMAT! Default Avatar
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    Post Thu Apr 12, 2007 7:45 am
    I'm still confused...because I thought the answer would be B but its C...

    RAGS Rising GMAT Star Default Avatar
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    Post Thu Apr 12, 2007 8:12 am
    Well here as u know the no of factors can be found out by getting the no of prime factors as u said (1+3)(y+1)

    statement 1 gives x=5 whickh is not sufficient since u need to know Y

    statement 2 gives y=3
    here consider the case where x=2 then we have no of factors will be
    for 2exp(6) will be (6+1) ie 7
    but for x as any prime other than 2 the ans would be (3+1)(3+1) ie 16

    but both together solves the problem by giving a value to X
    So C

    Cybermusings GMAT Destroyer! Default Avatar
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    Post Thu Apr 12, 2007 8:25 am
    Thanks RAGS...your explanation has lifted the cloud

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