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r is the radius

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r is the radius [#permalink] New post 04 Feb 2018, 15:20
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Question Stats:

92% (00:36) correct 7% (00:35) wrong based on 13 sessions


r is the radius of the sphere S and of the circle C

Quantity A
Quantity B
The ratio of the surface area of sphere S to the area of the circle C
4


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.

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[Reveal] Spoiler: OA

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Re: r is the radius [#permalink] New post 04 Feb 2018, 18:35
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Firstly, let me just remark that problems by McGraw-Hill are generally terrible. So don't take them as a very accurate gauge of how the GRE works.

For example, you DO NOT need to memorize the surface area of a sphere. But that's the only way to solve this question. On a related note, you don't need to know the volume of a sphere, surface area of a cone, or volume of a cone. Now, a real GRE question might tell you that the surface area of a sphere is 4πr^2, and then ask you to use it. But you don't need to memorize it.


So this problem can be solved by dividing the surface area of the sphere by the area of the circle, which gets us 4πr^2/πr^2. Since everything cancels out but the 4, we're left with 4 as the ratio. Thus the answer is C.
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Re: r is the radius [#permalink] New post 05 Feb 2018, 02:58
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SherpaPrep wrote:
Firstly, let me just remark that problems by McGraw-Hill are generally terrible. So don't take them as a very accurate gauge of how the GRE works.

.



Hi SherpaPrep,

Do you mean that we can totally skip Mcgraw Hill ques?
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Re: r is the radius [#permalink] New post 05 Feb 2018, 22:30
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Pranab-
While I wouldn't say they're totally worthless, there are so many other sources of problems out there that are better that I'd at least put McGraw-Hill at a very low priority. Kaplan is better, Princeton Review is better, Magoosh is better, official ETS questions are obviously the best... I can't imagine that most students would require more problems than the aforementioned 4 companies can provide.

The reason I say McGraw-Hill is so bad is that I've seen numerous problems of theirs that test concepts that aren't tested on the GRE. Or they have answer choices that are entirely unrealistic in that some of them are too obviously wrong or they are so incredibly far apart than anyone could just guess the answer by its size rather than doing any work. Many of them are solvable in one step, which is infrequently seen on the GRE. A lot of them contain mistakes or are just wrong. All of these issues can cause problems for students who are not aware that they're studying things they don't need to study, or are being convinced that the GRE's problems are easier than they really are, etc. So in a sense, doing McGraw-Hill problems could possibly make GRE students worse, rather than better. At the very least they'd be better served doing problems from other sources.

I may be making some fairly strong statements but I believe they are correct. The problem in this post is an example of what I'm talking about and I can easily be proven wrong if anyone can produce an official ETS question that requires the student to know the area of a sphere. Feel free to post it below. :)
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Re: r is the radius [#permalink] New post 05 Feb 2018, 22:52
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Thanks SherpaPrep for your comment
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Re: r is the radius [#permalink] New post 07 Feb 2018, 01:50
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Answer: 3 - since surface area of a sphere is 4πr^2
Re: r is the radius   [#permalink] 07 Feb 2018, 01:50
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