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Math Help - Dimensions of a rectangle

  1. #1
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    Dimensions of a rectangle

    Please help...

    A man has 40 meters of fencing material. What are the Dimensions of the largest recangular pen which he can enclose? What is the maximum area?

    Thank you!
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  2. #2
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    Quote Originally Posted by Ilovemath123 View Post
    Please help...

    A man has 40 meters of fencing material. What are the Dimensions of the largest recangular pen which he can enclose? What is the maximum area?

    Thank you!
    Let the dimensions of pen be a x b then as the perimiter is 40m we have:

    2a+2b=40

    or:

    b=20-a,

    so now the area of the pen is:

    A=a(20-a)

    and the maximum of a quadratic occurs midway between its roots, so the
    maximum area occurs when a=10m, but then b=10 and the pen is a square of
    area 100m^2.

    RonL
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