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GMAT PREP DS question

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alex.gellatly GMAT Destroyer! Default Avatar
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GMAT PREP DS question Post Mon Apr 16, 2012 1:52 am
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  • Lap #[LAPCOUNT] ([LAPTIME])
    If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

    (1) The remainder when p + n is divided by 5 is 1.

    (2) The remainder when p - n is divided by 3 is 1.

    Thanks in advanced

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    killer1387 GMAT Destroyer! Default Avatar
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    Post Mon Apr 16, 2012 2:01 am
    alex.gellatly wrote:
    If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

    (1) The remainder when p + n is divided by 5 is 1.

    (2) The remainder when p - n is divided by 3 is 1.

    Thanks in advanced
    (p+n)*(p-n)
    1) no info for 3 and p-n
    Insufficient

    2) no info for 5 and p+n
    insufficient

    1) and 2)
    we cant say anything about overall 15 for two (p-n) and (p+n)

    Hence E

    seal4913 Really wants to Beat The GMAT! Default Avatar
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    Post Mon Apr 16, 2012 6:25 pm
    alex.gellatly wrote:
    If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

    The question is what is the remainder when p^2 - n^2 is divided by 15. It's nice to see killer get it right even with the wrongly worded question Wink

    killer1387 GMAT Destroyer! Default Avatar
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    Post Tue Apr 17, 2012 1:50 am
    seal4913 wrote:
    alex.gellatly wrote:
    If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

    The question is what is the remainder when p^2 - n^2 is divided by 15. It's nice to see killer get it right even with the wrongly worded question Wink
    cant find anything wrongly worded. question is correct.
    If you are talking of p^2 and p2 then yeah i have seen posts here using the same representation so took it p^2 Smile

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