A few more marbles

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ph33l_da_l0v3
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A few more marbles

Postby ph33l_da_l0v3 » Mon Nov 06, 2006 9:25 pm UTC

Heres a puzzle I recall from quite some time ago... however i don't think i ever figured out the answer...

You have 12 marbles. One of the 12 is slightly heavier or slightly lighter then the others. You have one two plate scale, and you are allowed three weighings. Can you figure out which marble is slightly heavier or lighter?

I apologize if this one has been done on the forums before

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no-genius
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Postby no-genius » Mon Nov 06, 2006 10:35 pm UTC

So if I have 6 marbles in A and the other 6 in B, and A>B, how do I know if a marble in A is heavier or if a marble in B is lighter?
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ph33l_da_l0v3
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Postby ph33l_da_l0v3 » Mon Nov 06, 2006 11:29 pm UTC

You don't, and since you don't know if the abnormal marble is heavier or lighter, 6 v. 6 would tell you nothing.

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svk1325
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Re: A few more marbles

Postby svk1325 » Tue Nov 07, 2006 12:15 am UTC

ph33l_da_l0v3 wrote:You have 12 marbles. One of the 12 is slightly heavier or slightly lighter then the others.


Just clarification for the people who might mis-read the problem. As to my thoughts, I think this was on the forum a while ago, but I can't find it. The solution is more sophisticated than it would seem though. I can't remember it.

I'm trying to think of a solution... I found one that works 45~50% of the time. Problem is, that's not what we're looking for.
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Postby GreedyAlgorithm » Tue Nov 07, 2006 12:28 am UTC

GENERATION 1-i: The first time you see this, copy it into your sig on any forum. Square it, and then add i to the generation.


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