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OG QR 2nd Ed. DS #86

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tofubeans Just gettin' started! Default Avatar
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OG QR 2nd Ed. DS #86 Post Sat Apr 28, 2012 1:43 pm
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  • Lap #[LAPCOUNT] ([LAPTIME])
    If m and n are consevutive positive integers, is m greater than n?

    1) m-1 and n+1 are consecutive positive integers.

    2) m is an even integer.

    Solution: A

    The book's explanation is confusing me. They give two different outcomes for solution A yet it is still sufficient. I thought when there are two different outcomes/choices...that the data is insufficient?

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    Post Sat Apr 28, 2012 2:01 pm
    If m and n are consevutive positive integers, is m greater than n?

    Quote:
    1) m-1 and n+1 are consecutive positive integers.
    Let us assume that m<n. Since, m and n are consecutive positive integers and n>m, the value of n = m+1. The value of n+1 is m+2. but m+2(n+1)and m-1 are not consecutive integers(contradicts statement I). So, our assumption that the value of m is less than n is wrong.

    Now, let us assume that m>n. Since, m and n are consecutive positive integers and m>n, the value of m = n+1. and m(n+1)and m-1(n)are consecutive integers. So, our assumption that the value of m is greater than n is correct. So, statement I is sufficient to answer the question.

    Let me explain the same with an example.
    Let m<n, m=5 and n=6. Then the value of m-1 is 4 and that of n+1 is 7. Since 4 and 7 aren't consecutive integers, the value of m cannot be less than the value of n.

    Let m>n, m=6 and n=5. Then the value of m-1 is 5 and that of n+1 is 6 (consecutive positive integers).
    Quote:
    2) m is an even integer.
    Irrelevant!

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    pemdas GMAT Titan Default Avatar
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    Post Sat Apr 28, 2012 2:41 pm
    this question is very precise in its formulation. You are given double constraints here: one in prompt m,n consecutive positive integers and the other in statement(1) m-1,n+1 are consecutive positive integers. The only way this is possible must be when m>n and two consecutive integers interchange their places.
    tofubeans wrote:
    If m and n are consevutive positive integers, is m greater than n?

    1) m-1 and n+1 are consecutive positive integers.

    2) m is an even integer.

    Solution: A

    The book's explanation is confusing me. They give two different outcomes for solution A yet it is still sufficient. I thought when there are two different outcomes/choices...that the data is insufficient?

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    ronnie1985 GMAT Destroyer!
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    Post Sat Apr 28, 2012 11:01 pm
    Assume m<n => n=m+1, then using the info in S1, we get m<n, hence not possible
    Assume m>n => m=n+1, then using the info in S1, we get m>n, hence possible and sufficient..

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    Anurag@Gurome GMAT Instructor
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    Post Sun Apr 29, 2012 10:35 am
    tofubeans wrote:
    If m and n are consevutive positive integers, is m greater than n?

    1) m-1 and n+1 are consecutive positive integers.

    2) m is an even integer.

    Solution: A

    The book's explanation is confusing me. They give two different outcomes for solution A yet it is still sufficient. I thought when there are two different outcomes/choices...that the data is insufficient?
    (1) m - 1 and n + 1 are consecutive positive integers implies m > n.
    If m < n, then m - 1 and n + 1 wouldn't be consecutive; SUFFICIENT.

    (2) m is an even integer; clearly NOT sufficient.

    The correct answer is A.

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    shagalo Just gettin' started! Default Avatar
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    Post Sun Jun 02, 2013 4:20 pm
    the problem in this question is , in the choice # 1 , they said : m-1 and n+1 are consecutive positive integers.
    How do i know that m-1 is before n+1 or after ,,,, they said just ( consecutive integers)

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