PS(Geometry)

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rintoo22 Rising GMAT Star Default Avatar
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PS(Geometry) Post Sat Apr 06, 2013 12:20 pm
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  • Lap #[LAPCOUNT] ([LAPTIME])
    The sides of a square region, measured to the
    nearest centimeter, are 6 centimeters long. The
    least possible value of the actual area of the
    square region is
    A.36.00 sq cm
    B.35.00 sq cm
    C.33.75 sq cm
    D.30.25 sq cm
    E.25.00 sq cm

    How to approach such questions ?

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    Post Sat Apr 06, 2013 1:02 pm
    rintoo22 wrote:
    The sides of a square region, measured to the
    nearest centimeter, are 6 centimeters long. The
    least possible value of the actual area of the
    square region is
    A.36.00 sq cm
    B.35.00 sq cm
    C.33.75 sq cm
    D.30.25 sq cm
    E.25.00 sq cm

    How to approach such questions ?
    The key information here is measured to the nearest centimeter.
    So, the sides do not necessarily have length 6.
    In fact 5.5 < (length of 1 side) < 6.5

    We want the smallest possible area. This will occur when the side lengths are minimized.
    The shortest length of each side is 5.5 cm.
    So, the smallest possible area = (5.5)(5.5) = 30.25 = D

    Cheers,
    Brent

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    srcc25anu GMAT Destroyer! Default Avatar
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    Post Sat Apr 06, 2013 1:14 pm
    SIde of square measured to nearest integer = 6
    therefore the size could range from 5.5 - 6.4
    for area of this square to be the smalles we should consider the smallest number which is 5.5
    and if side = 5.5, area of square = 5.5 * 5.5 = 30.25
    Hence D

    bharat.bondalapati Just gettin' started! Default Avatar
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    Post Sun Apr 07, 2013 5:02 am
    30.25

    Key info is "measured to the nearest cm". Since, we need the least area possible for the square the least side length possible is 5.5. Hence, least area possible is 30.25cm^2

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    Post Sun Apr 07, 2013 5:16 am
    As an aside, notice that the question requires us to find (5.5)^2
    This is the same as squaring 55 to get 3025 and then moving the decimal over 2 spaces to get 30.25

    If anyone is interested, there's a 3-second technique for squaring numbers ending in 5. To learn this technique, watch our free video: http://www.gmatprepnow.com/module/gmat-powers-and-roots?id=1024

    Cheers,
    Brent

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    Use our video course along with Beat The GMAT's free 60-Day Study Guide

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