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Divisble by 5

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dipzzz Just gettin' started! Default Avatar
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Divisble by 5 Post Sun May 06, 2012 8:26 am
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  • Lap #[LAPCOUNT] ([LAPTIME])
    x is a positive number. If 9^x + 9^x+1 + 9^x+2 + 9^x+3 + 9^x+4 + 9^x+5 = y, is y divisible by 5?
    1) 5 is a factor of x.
    2) x is an integer.


    isn't the question stem sufficient??

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    Bill@VeritasPrep GMAT Instructor
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    Post Sun May 06, 2012 9:27 am
    We need to know that x is an integer. If x is a decimal, then we could end up with decimal values for our terms, i.e. 9^2.2=~125.7

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    klmehta03 Rising GMAT Star Default Avatar
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    Post Sun May 06, 2012 12:53 pm
    IMO A .
    OA pls?

    dipzzz Just gettin' started! Default Avatar
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    Post Sun May 06, 2012 9:33 pm
    OA D

    bryan88 Really wants to Beat The GMAT! Default Avatar
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    Post Fri May 11, 2012 10:15 pm
    Dont we get 9^(x) *66430 on expansion.

    This is anyway divisible by 5.

    Am i missing something?

    lathmanu Just gettin' started! Default Avatar
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    Post Sat May 12, 2012 1:48 am
    bryan88 wrote:
    Dont we get 9^(x) *66430 on expansion.

    This is anyway divisible by 5.

    Am i missing something?
    Yes the Question can be written as 66430*(9^x)

    I would refer to Bill's reply.
    We need to know that x is an integer.

    Bill@VeritasPrep wrote:
    We need to know that x is an integer. If x is a decimal, then we could end up with decimal values for our terms, i.e. 9^2.2=~125.7
    I first took B as the answer.
    But after seeing the original answer as D, I realized that if 5 is a factor of x, then x is an integer.
    A is also sufficient.

    Thanks for the question dipzzz

    ihatemaths Really wants to Beat The GMAT! Default Avatar
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    Post Sat May 12, 2012 6:30 am
    how do you people get 66430 ? did you compute fully ?

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