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Re: The Ultimate Q51 Guide [Expert Level]
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04 Jul 2016, 22:59
A Geometry question can be difficult as well
(ex 6) A rectangular iron plate is 12 feet by 8 feet. We can make a right circular cylinder by rolling the length side of the plate or the width side of the plate. If the cylinder’s volume is at its greatest, which one of the length or the width of the iron plate is the circumference of the cylinder and what is the difference between 2 volumes of cylinders made by rolling?
A. the circumference is 8, the difference is 54/π
B. the circumference is 8, the difference is 96/π
C. the circumference is 12, the difference is 84/π
D. the circumference is 12, the difference is 96/π
E. the circumference is 12, the difference is 86/π
==> As the number increases fast when it is squared, the volume increases faster when it is being rolled at 12-inches side. Hence, from 2πr=12, we get r=6/π. Hence, π(6/π)2(8)=288/π. The volume of the cylinder rolled at the 8-inches side is – from 2πr=8, we get r=4/π – π(4/π)2(12)=192/π. The difference is 288/π-192/π=96/π. Hence, the correct answer is D.
Answer: D