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math

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faye has 20 feet of fencing to make a rectangular pen for her dog.What is the largest area she can fence in?

  • math -

    20 feet

  • math -

    is that right im just gessing

  • math -

    Let's see --
    it could be 5 + 5 + 5 + 5
    or 4 + 4 + 6 + 6
    or 3 + 3 + 7 + 7

    Find the areas of these pens.

    A = length times width

    So -- a 3 foot by 7 foot pen would be 21 square feet.

    Find the areas of the other two pens. Which gives you the most square feet?

  • math -

    For a math question:
    Make a table of width (W) and lengths (L) that add up to 20 for perimeter = 2(W+L).
    Calculate the area for each line. Choose the biggest area.
    Width Length Area
    1 9 9
    2 8 16
    3 7 21
    4 6 24
    .....
    8 2 16
    9 1 9

    For a calculus question:
    Let W=width, then
    (10-W)=length, and
    Area=A(W)=W(10-W)=10W-W²
    For maximum or minimum:
    dA/dW=10-2W=0, or W=5
    d²A/dW²=-2 <0 so maximum.
    A(5)=5(10-5)=25 (maximum area)

  • math -

    hi im only in 4th grade so i really kind of need simple answers

  • math -

    Please see my answer. I'm sure you can figure out your answer using that information.

  • math -

    thanks ms.sue u rock

  • math -

    You're welcome, Alex. :-)

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