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A contractor has installed a silt fence around an area that is semi-circular and level to prevent soil from the construction site entering nearby streams. The diameter of the semi-circle is 900 feet. How many linear feet of fence does the contractor need to use to enclose the area? How many acres are within the enclosed by the fence? I need an answer for part two of the question.

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Are you trying to solve by yourself or only pasting the problem here? –  Sigur Feb 5 '13 at 0:41
    
I tried to solve it but i am having problems with the second part. thanks –  Sami Alshehry Feb 5 '13 at 0:42
    
So you can write what you did ans we can give you some hints. –  Sigur Feb 5 '13 at 0:43
    
Area of a whole circle =$\pi r^2$, and according to Google 43560 square ft to an acre. –  Maesumi Feb 5 '13 at 0:45
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Welcome to MSE! I'd like to tell you a few things that will likely improve the reception of your question. Your title does not indicate the content of the problem. Nor does your tag. This means that people have no way of knowing that they're interested in your problem (unless they click on it, but why would they when there are other, better indicated problems?). You have also just copy-pasted the question. Many people here expect you to put in some effort before they put in the effort to help. –  mixedmath Feb 5 '13 at 0:47
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1 Answer

Area of the whole circle is $\pi r^2=\pi 450^2$. For a semi circle it is $\pi 450^2/2$. In acres this is $\pi 450^2/(2*43560)=7.30$

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