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Math Help - [SOLVED] Area help

  1. #1
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    [SOLVED] Area help

    A = /360 x r

    If A= 15m and = 90 . Find r

    Please help, I don't know how to work backwards

    The shape is a sector
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wato View Post
    A = /360 x r

    If A= 15m and = 90 . Find r

    Please help, I don't know how to work backwards
    A=\frac{\theta}{360^{\circ}}\times \pi r^2

    They give you A and \theta...

    So plugging them into the equation, you have

    15~m^2=\frac{90^{\circ}}{360^{\circ}}\times \pi r^2

    Now just solve the equation for r:

    15~m^2=\tfrac{1}{4}\pi r^2\implies 60 ~m^2=\pi r^2\implies r=\dots

    Try to figure out the rest.

    I hope this helps!

    --Chris
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  3. #3
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    Thanks man, that really helped

    er, one more question; if i were to have half a circle with the area being 15m and i needed to find the radius. what would the equation be?

    A= r/2 ?
    Last edited by wato; September 4th 2008 at 04:12 PM.
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  4. #4
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wato View Post
    Thanks man, that really helped

    er, one more question; if i were to have half a circle with the area being 15m and i needed to find the radius. what would the equation be?

    A= r/2 ?
    A=\tfrac{1}{2}\pi r^2



    --Chris
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