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OA is different than what I get

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jainan24
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OA is different than what I get [#permalink] New post   03 Jan 2007, 23:14
OA is different than what I get



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Re: OA is different than what I get [#permalink] New post   03 Jan 2007, 23:49
C for me

whats the OA ?
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Re: OA is different than what I get [#permalink] New post   04 Jan 2007, 01:29
I also got C

V=pi(r^2)*h

h=7
r=3

V=pi9*7=63pi
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Re: OA is different than what I get [#permalink] New post   04 Jan 2007, 04:14
jainan24 wrote:
OA is different than what I get


I got E. Can't we have a cylinger with height 6 and radius 3.5(the base sitting on the 8x7 side)?

That gives us pi*(3.5)^2*6 = 73.5pi.
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Re: OA is different than what I get [#permalink] New post   04 Jan 2007, 06:42
hsampath wrote:
jainan24 wrote:
OA is different than what I get


I got E. Can't we have a cylinger with height 6 and radius 3.5(the base sitting on the 8x7 side)?

That gives us pi*(3.5)^2*6 = 73.5pi.


I agree.

For a cylendar, we obtain more volume by increasing the radius than by the height. :).... It's due to the root done on the radius : any increase is shapped by the curve x^2 not by a linear rule.
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Re: OA is different than what I get [#permalink] New post   04 Jan 2007, 07:36
OA is E, I guess the rule of thumb is first take the face with two largest sides (8 and 7), pick the diameter as smaller of two and then pick the height as the shortest side
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Re: OA is different than what I get [#permalink] New post   06 Jan 2007, 12:22
jainan24 wrote:
OA is E, I guess the rule of thumb is first take the face with two largest sides (8 and 7), pick the diameter as smaller of two and then pick the height as the shortest side


Got E as well.

I think that to find the cylinder with the largest volume takes a bit more. Let´s say we have a rectangle box, container, etc. with a<b<c. The possible volumes would be

pi * (a/2)^2 * c
pi * (b/2)^2 * a
pi * (a/2)^2 * b

The 1st and the 2nd are always greater than the third. Now, between the 1st and the 2nd, we´d have to find out whether a^2 * c is < = > than b^2 * a, or, simplifying, whether a * c is < = > than b^2.
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Re: OA is different than what I get [#permalink] New post   07 Jan 2007, 07:24
I agree with Andr359.

For example, the largest cylinder for a cube of sides 4, 6 & 10.

would be obtained by pi * 2^2 * 10 = 40pi and not pi * 3^3 * 4 = 36pi
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Re: OA is different than what I get [#permalink] New post   07 Jan 2007, 18:49
I think instead of cube we call it cuboid or rectangular Parallelepiped

andr359 is right
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Re: OA is different than what I get [#permalink] New post   09 Jan 2007, 14:50
I have seen another one of these. They try to trick you with the the height. Just need to ignore spatial relations and take half the smaller of the largest two dimensions, square it and multiply by pi and third dimension.

Eric
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Re: OA is different than what I get [#permalink] New post   10 Jan 2007, 19:58
largest possible radius 7/2

so pi*6*7^2/4 = pi*49*3/2 = pi*73.5


E



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Re: OA is different than what I get [#permalink]
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