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Identifying the radius and height of a cylinder - IR

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by gmattesttaker2 » Thu Aug 22, 2013 9:13 pm
Hello,

Can you please help with this IR question from MGMAT? Thanks for your help.


OA:

Column 1: The correct answer is D.
Column 2: The correct answer is B.
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by [email protected] » Thu Aug 22, 2013 11:36 pm
Hi gmattesttaker2

This question requires you to know the Volume formula for cylinders: (pi)(radius)^2(height)

We want to MAXIMIZE the volume under the following rules (laid out by the question):

The radius can be up to twice the height (or vice versa)
The greatest that the sum of the radius and the height can be is 16

Based on the volume formula, the way to maximize the volume is to maximize the radius (since that value is squared). We CAN'T have the radius = 11, because that would make the height 5 (or less) and that BREAKS the "up to twice" rule.

We CAN have a radius of 10 though; with that radius, we can put everything else into the height, which would be = 6

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