## Surface area of the balloon

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### Surface area of the balloon

by Baldini » Tue Apr 28, 2009 3:40 am
The volume of a sphere with radius r is (4/3)&#960;r^3 and the surface area is 4&#960;r^3. If a spherical balloon has a volume of 972&#960; cubic centimeters, what is the surface area of the balloon in square centimeters?

(A) 324
(B) 729
(C) 243&#960;
(D) 324&#960;
(E) 729&#960;

(&#960; = pi)
OA is D.

thanks
GMAX

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by sacx » Tue Apr 28, 2009 4:49 am
I think surface area should be 4&#960;r^2

We can find the radius of the balloon

(4/3)&#960;r^3 = 972&#960;
r^3 = 972 * 3/4
r = 9

Surface area = 4&#960;r^2 = 4*&#960;*9^2 = 324&#960;
SACX

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by Neo2000 » Tue Apr 28, 2009 4:50 am
Surface area of a sphere is 4(pi)r^2

You've got volume of a sphere. From that you can find r.

Once you have r, you can find th surface area.

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by Baldini » Tue Apr 28, 2009 5:09 am
Thank you very much for your responses - but just to be sure, I have attached a screenshot of the original question (and will assume it was a typing error).
Attachments
mistype.doc