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napkin ring

by ousek » Mon Jul 27, 2009 2:45 pm
Hey, GMAT beaters...

Here is a riddle you could find in the GMAT:

I made a cylindrical hole in a perfect sphere with an electric drill, and took out the two extremities of the sphere to get a nice napkin ring. Mum is very happy!

Image

Cut, my napkin ring is now 6cm high.

:arrow: What is its volume ?

The answer after your explanations ! :wink:

Enjoy !

Ousek
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by ASS1991 » Mon Jul 27, 2009 5:55 pm
Nice question, but don't we need the radius/diameter or any other information?
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by PussInBoots » Mon Jul 27, 2009 8:30 pm
Your mom won't be proud of your low GMAT score because this is very dumb question...
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by ousek » Fri Jul 31, 2009 2:30 pm
ASS1991 wrote:Nice question, but don't we need the radius/diameter or any other information?
No, there is no further information available !
Nevertheless, one can find the answer... :wink:
PussInBoots wrote:Your mom won't be proud of your low GMAT score because this is very dumb question...
A dumb question, yes, perhaps! But I wonder why you don't answer, in this case! :lol: I guess you should try an answer...

:arrow: Come on guys, let's think about it...
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by nestlepurelife » Fri Jul 31, 2009 4:09 pm
https://en.wikipedia.org/wiki/Napkin_ring_problem

I doubt it will be on the GMAT. However, for the curious, I've linked the idea behind this problem.
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by ousek » Fri Jul 31, 2009 4:48 pm
Neither do I.
As far as I am concerned, I solved this problem in few minutes, even if I didn't have the knowledge explained in your link (thank you for it). Nevertheless, no question should require "few minutes".

I just posted it because I believe it make people search... and the more a brain works, the faster it goes!
Plus, I believe same of you here would have enjoyed such a riddle...
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by tohellandback » Fri Jul 31, 2009 4:56 pm
Is it 36pi? and I have a very very simple solution.

Just imagine that the length you cut is almost equal to 0. In that case the diameter of the sphere will be 6
and the volume of the sphere is 4/3 * pi* 3^3 =36pi

of course it took me more than 5 minutes to figure out this solution.

and IMO it might not not be on GMAT or a question like this..but it is certainly not a "dumb" question
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by ousek » Sat Aug 01, 2009 2:22 pm
:lol: tohellandback, you got it !

This is exactly the way one should solve the problem. The other way being, of course, to write three pages of calculus...
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