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(2): solution to B by pleasance)

Please accept my apologies. You're right. This particular problem only requires us to identify the 'fake' coin, not the type of 'fakeness'.

The general solution I have provided is for the more difficult problem of not only identifying the 'fake' coin but also identifying if the 'fake' coin is heavier or lighter than the rest.

I should've been more careful while reading the problem.

Posted by Sanjay on 2003-05-19 09:00:57