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Cylinder A, which has a radius of x and a height of y, has a greater

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Cylinder A, which has a radius of x and a height of y, has a greater [#permalink]

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New post Updated on: 01 Oct 2015, 00:56
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Geometry MGMAT Question Bank Q24

Cylinder A, which has a radius of x and a height of y, has a greater surface area than does Cylinder B, which has a radius of y and a height of x. How much greater is the surface area of Cylinder A than that of Cylinder of B?

Though options are not available, still it's a good questions.
[Reveal] Spoiler: A
x/y

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Originally posted by rohitmanglik on 30 Sep 2015, 23:40.
Last edited by Bunuel on 01 Oct 2015, 00:56, edited 1 time in total.
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Re: Cylinder A, which has a radius of x and a height of y, has a greater [#permalink]

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New post 01 Oct 2015, 19:39
rohitmanglik wrote:
Geometry MGMAT Question Bank Q24

Cylinder A, which has a radius of x and a height of y, has a greater surface area than does Cylinder B, which has a radius of y and a height of x. How much greater is the surface area of Cylinder A than that of Cylinder of B?

Though options are not available, still it's a good questions.
[Reveal] Spoiler: A
x/y


Hi,
you require to reword your question or change the answer...
1. Q-- what is the ratio of surface area of cylinder A to cylinder B?..... Ans\(\frac{x}{y}\)
2. for your Q, the answer will \(2pi(x^2-y^2)\)...... How can you have an answer without 2 pi, when both the quantity have 2pi in it...
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Re: Cylinder A, which has a radius of x and a height of y, has a greater [#permalink]

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Cylinder A, which has a radius of x and a height of y, has a greater surface area than does Cylinder B, which has a radius of y and a height of x. How much greater is the surface area of Cylinder A than that of Cylinder of B?



Hi! Well your question is a little bit ambiguous... However, as you mentioned, it is a good question.
So let’s try to get areas of Cylinder A and B.
First of all a Cylinder has two circles(bottom and top) and a rectangle(side) so the area of Cylinder A is 2*pi*x^2 + 2*pi*x*y.
Similarly the area of Cynlinder B is 2*pi*y^2 + 2*pi*x*y.

Since Cylinder A has a greater surface area than does Cylinder B, x > y.
So the difference of area is 2*pi*x^2 + 2*pi*x*y -(2*pi*y^2 + 2*pi*x*y) = 2*pi(x^2 –y^2)
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Re: Cylinder A, which has a radius of x and a height of y, has a greater [#permalink]

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New post 30 Mar 2018, 05:27
The surface area of a cylinder = 2 r2 + 2 rh , where r = the radius and h = the height.

Surface area of Cylinder A = 2 x2 + 2 xy

Surface area of Cylinder B = 2 y2 + 2 xy

Surface area of Cylinder A – surface area of Cylinder B =

2 x2 + 2 xy – (2 y2 + 2 xy) = 2 (x2 – y2)
Re: Cylinder A, which has a radius of x and a height of y, has a greater   [#permalink] 30 Mar 2018, 05:27
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