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the circle C

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the circle C

by sanju09 » Tue May 26, 2009 12:48 am
What is the circumference, in inches, of circle C?

(1) When a circle, which is ½ in radius to circle C is removed from the circle C, the remaining area is 7.45 square inches.

(2) The ratio of the surface area of the sphere (same in radius to circle C) to the area of the circle C is 4:1.



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Source: — Data Sufficiency |
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by eyoussef » Tue May 26, 2009 1:04 am
I think the answer is A

(1)the satement says that the big cirlce has radius r and the small circle has radius 1/2 r
thus area of big circle - area of small cirlce = pi*r^2 - pi*(1/2*r)^2
3/4*pi^2 = 7.45, r could be obtained from the equation SUFFICIENT

(2) this statement means :
(4*pi*r^2)/Pi*r^2 = 4/1
INSUFFICIENT

some one please correct me if i'm wrong
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by caprion » Tue May 26, 2009 8:23 am
I agree with eyoussef :)
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by TryHarder » Tue May 26, 2009 12:05 pm
Just to add: 2. just restates a universal fact hence would not help.
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