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Math Help - Non-Linear Modelling Concrete Slab Problem

  1. #1
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    Non-Linear Modelling Concrete Slab Problem

    I hope someone can help me because i'm stumped

    This problem is in the maths applied level 3 & 4.

    The concrete slab in the shape of a rectangle shown on the right has an area of 63m^2. Form a Quadratic Equation and solve for "x" and then determine the width and length of the rectangle in order for it to be paved.

    (you can't use trial and error or guessing)




    Hope Someone can help me out

    Cheers OLLiE
    Last edited by ollieman; October 24th 2007 at 11:13 PM. Reason: fix up the picture
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  2. #2
    MHF Contributor
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    The slab is rectangle, so,
    Area, A = 3x(x+4) = 63
    3x^2 +12x -63 = 0
    Divide both sides by 3,
    x^2 +4x -21 = 0
    Factoring,
    (x +7)(x -3) = 0
    x = -7 or 3 meters

    Now I see what you mean by "in order for it to be paved"

    The x = -7 meters cannot be measured because there are no negative measurements.

    So, x = 3m

    Therefore,
    width = 3x = 3*3 = 9m.
    lenght = (x +4) = (3 +4) = 7m.

    Umm, again, therefore, width = 7 meters, and length = 9 meters. ---answer.
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  3. #3
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    thanks ticbol

    thanks heaps ticbol

    I'm just not yet very good at written problems.
    I'm sure you didn't even have to think to blink to work it out.

    Cheers OLLiE
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