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Many coins - one fake (Posted on 2003-05-14) Difficulty: 5 of 5
Given a balance scale that is sure to break after X weighings, find an equation for the largest number of coins N, from which you can determine a fake coin that has the wrong weight if

A: You know whether the fake is lighter or heavier

B: You do not know whether the fake is lighter or heavier

(Assume only one of the N coins is fake)

See The Solution Submitted by Jonathan Waltz    
Rating: 3.7143 (7 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: solution to B | Comment 12 of 20 |
(In reply to solution to B by pleasance)

I'd be interested in seeing what the strategy is for any of these. I ask in light of Sanjay's comment to this and also to the 39 Coins problem, where he shows that not all information-theoretic possibilities are really possible. So I think there might be a flaw in what strategies you have found that allow more than n = (3^x-3)/2.
  Posted by Charlie on 2003-05-18 04:48:18

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