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Starr_DynastyT
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@shamil98
stupidinmath
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A= big semicircle.. what's next?
MayankD
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50pi
MayankD
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Just remove the semicircle on the left and place it in the gap on the right
oldrin.bataku
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this is SAT yes? I remember this one
Haleo
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\[a= \pi*r ^{2}\]
\[a= ( \pi * 10^{2} ) /2 = 157.079\]
Haleo
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Isn't it right?
oldrin.bataku
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|dw:1389510061781:dw|
oldrin.bataku
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|dw:1389510085539:dw|
oldrin.bataku
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|dw:1389510103621:dw|
so the area is equivalent to just the top semicircle... we merely moved the piece under the line to fill the hole to the right
oldrin.bataku
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the radius is very clearly \(r=10\) ergo the area is \(A=\pi r^2=\pi(10)^2=100\pi\)
oldrin.bataku
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|dw:1389510292746:dw|
liliegirl
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It is a semicircle so you need to divide by 2. The answer is 50pi + 25pi over 2.
\[\frac{ 75\pi }{ 2 }\] is the answer.
oldrin.bataku
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oops -- good catch. you do need to multiply by \(1/2\) to get just the top:$$\frac12\cdot100\pi=50\pi$$that being said, it is NOT \(\frac12(50\pi+25\pi)\)
liliegirl
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|dw:1389510798177:dw|
stupidinmath
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so.. also find that part and add it?
liliegirl
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You need to add that because it is also shaded.
The area of that part is 25pi over two.
oldrin.bataku
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@liliegirl that part is precisely the part we moved to fill in the top semicircle. it is now accounted for...
stupidinmath
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oh. right
stupidinmath
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so.. the answer is.. 314.16 right?
thanks guys
liliegirl
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@oldrin.bataku
Ahhh, Sorry, I didn't notice.... :)))
oldrin.bataku
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@stupidinmath no it's half of that, i.e. \(50\pi\)
stupidinmath
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oh.. since its a semi circle.. k thanks :)