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Math Help - Area of a Rectangle

  1. #1
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    Area of a Rectangle

    Having trouble with this seemingly simple problem, help is much appreciated!

    Three sides of a fence and an existing wall form a rectangular enclosure. The total length of fencing used for the three sides is 240 ft. Let x be the length of each of the two sides perpendicular to the wall.
    a. Draw a picture and write a formula for the area of the enclosure.
    b. Then find the value for x that would give an area of 5500 ft^2

    a. Pictures easy but would the formula for the area of the rectangle be x times y = 5,500?

    b. Don't really know how to find the exact value for x, so I just used trial and error to find x to be around 214.35 and y to be around 25.65.

    Help with finding the exact value and the formula would be great.
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  2. #2
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    A = L \times W

    where L = x, W = y

    and we know 2x+y=240 so y= 240-2x

    therefore A = x\times (240-2x)

    5500 = x\times (240-2x)

    5500 = 240x-2x^2

    0 = 240x-2x^2-5500

    now solve the quadratic
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