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Data Sufficiency questions 700 level - problem

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ashwinhirawat Just gettin' started! Default Avatar
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Data Sufficiency questions 700 level - problem Post Sun Apr 22, 2012 2:15 pm
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  • Lap #[LAPCOUNT] ([LAPTIME])
    |x| + |y| = 32 ; what is the value of xy ?

    1. -4x - 12y = 0

    2. |x| -|y| = 16

    I solved it as follows -

    Statement 1:
    x = -3y
    Original Statement :
    x + y = 32 Using statement 1. y = -16
    -x +y = 32 Using Statement 1. y = 8
    x - y = 32 Using Statement 2. y = -8

    And so 1 is not sufficient . However the Original Answer is A

    They do not consider all 3 cases that I did. Is it wrong to consider all the cases as I did ?

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    seal4913 Really wants to Beat The GMAT! Default Avatar
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    Post Sun Apr 22, 2012 4:12 pm
    If x = -3y.

    Then you have |x| or |-x|. So |-3y| = 3y and |-(-3y)| = 3y

    hackscript Just gettin' started! Default Avatar
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    Post Mon Apr 23, 2012 5:24 am
    Considering (1)
    x=-3y, so if x is positive y is negative

    Considering x positive: x-y=32 and x=-3y solving, y=-8 and x=24
    Considering x negative: -x+y=32 and x=-3y solving, y=8 and x=-24

    The product is the same so (1) is suf

    Considering (2)

    Adding both equations, x=24 or x=-24 and so y=8 or y=-8
    Can't no if product is 8*24 or -8*24

    so (2) is insuf

    Answer: A

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    Post Mon Apr 23, 2012 5:40 am
    I posted an explanation here:

    http://www.beatthegmat.com/if-x-t87263.html

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