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Math Help - geometry help... please!

  1. #1
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    geometry help... please!

    This seems really basic to everything else I see posted... hopefully I can get some help.. asap Thank you!

    A circular window has an area of 10 square feet. Find the circumference of the window.
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  2. #2
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    The area of a circle is given by:
    A = \pi r^2

    The circumference of a circle is given by:
    C = 2\pi r

    Find the radius from the given area, then find the circumference.
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  3. #3
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    thank you.. I guess I need a little more help, cause I have that info, I am not sure how to do that part though.

    I have the area at 10 ft ^2
    so how do I figure the circumference with that? I guess first figure out the radius? and how do I do that?

    thank you so much! really.. sorry for needing more help... hope you can help me!
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  4. #4
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    Quote Originally Posted by mathmom View Post
    thank you.. I guess I need a little more help, cause I have that info, I am not sure how to do that part though.

    I have the area at 10 ft ^2
    so how do I figure the circumference with that? I guess first figure out the radius? and how do I do that?

    thank you so much! really.. sorry for needing more help... hope you can help me!
    Solve 10 = \pi r^2 for r: r^2 = \frac{10}{\pi} \Rightarrow r = \, ....

    Then substitute the value for r into C = 2 \pi r.
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  5. #5
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    Thank you.. could you check this and see if it is correct?
    r^2=10/pi
    3.183098862=r^2

    20=2(pi)(3.183098862)
    so the cirucumference is 20? is that right?
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  6. #6
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    You substituted r^2 instead of r, which is wrong.

    r^2 = \frac{10}{\pi}

    r = \sqrt{\frac{10}{\pi}} \approx 1.78412411615
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