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)

(In reply to re: Weighty Solution (maybe!) by Chris)

I don't think it would work for 3 weighings on B. You would only be able to use X if its divisible by 2.

I would propose N=2^(2*floor(X/2))

And the formula works for 0 too. If you couldn't use the scale at all, the most coins you could have was 1, and that's the fake coin!

Posted by Gamer on 2003-05-14 12:22:35