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Difficult Math Problem #91 - Range

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800guy GMAT Destroyer! Default Avatar
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Difficult Math Problem #91 - Range Post Mon Jan 29, 2007 10:24 am
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  • Lap #[LAPCOUNT] ([LAPTIME])
    if -2=<x=<2 and 3<=y<=8, which of the following represents the range of all possible values of y-x?

    (A) 5<=y-x<=6
    (B) 1<=y-x<=5
    (C) 1<=y-x<=6
    (D) 1<=y-x<=10
    (E) 1<=y-x<=10

    from diff math problems doc. OA coming when some people provide answers/explanations

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    jayhawk2001 Community Manager
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    Post Mon Jan 29, 2007 11:44 pm
    Min y-x = min y - max x = 3-2 = 1
    Max y-x = max y - min x = 8-(-2) = 10

    So range seems to be 1 through 10.

    I can't make out the difference between options D and E though.

    800guy GMAT Destroyer! Default Avatar
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    Post Wed Jan 31, 2007 10:09 pm
    here's the OA:

    you can easily solve this by subtracting the two inequalities. To do this they need to be in the opposite direction; when you subtract them preserve the sign of the inequality from which you are subtracting.

    3 < y < 8
    multiply the second one by (-1) to reverse the sign
    2 > x > -2
    Subtract them to get
    3 - 2 < y - x < 8 - (-2)
    1 < y - x < 10

    gmatguru Just gettin' started! Default Avatar
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    Post Sun Feb 04, 2007 1:39 am
    Hey can anyone tell me wht is this difficult maths doc?

    800guy GMAT Destroyer! Default Avatar
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    Post Mon Feb 05, 2007 3:49 pm
    gmatguru wrote:
    Hey can anyone tell me wht is this difficult maths doc?
    hi guru, you can find it on the gmat resource wiki. it's just a word doc with the toughest gmat practice problems

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