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Take the right one (Posted on 2013-10-18) Difficulty: 3 of 5
Among 100 coins exactly 4 are fake. All genuine coins weigh the same; all fake coins, too. A fake coin is lighter than a genuine coin.

How would we find at least one genuine coin using two weighings on a balance scale?

Source: 2010 Euler math Olympiad in Russia- authored by A.Shapovalov

No Solution Yet Submitted by Ady TZIDON    
Rating: 3.0000 (1 votes)

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re: Solution | Comment 6 of 18 |
(In reply to Solution by xdog)

That doesn't quite work.  Say that the first weighing balances, and 12 are LL.  Then suppose that coins 34 are NN.  12< 34, but there's still an L somewhere in the pile of 47 coins.


Interesting puzzle, will think about it.

  Posted by Tristan on 2013-10-19 03:38:57
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