have 12 coins, one of which is counterfeit, and a balance pan
scale. The fake coin may be identified by the fact that it's
weight is different from the 11 genuine coins. Can you identify
the counterfeit coin and whether it is heavier or lighter in
three Background & Techniques This is an old problem with lots
of literature available on the web. The best reference is
probably from one of Martin Gardner's Mathematical Recreations
columns published in Scientific American magazine about 40 years
ago. It apparently was reprinted in book form in "Sixth Book of
Mathematical Games from Scientific American" which is
unfortunately out of print. I have copied a pretty good summary
of the algorithm from the alt.rec.puzzles newsgroup to this
page: This program implements the Gardner algorithm to solve the
problem (or check your solution) for this problem or the simpler
case when you know whether the coin is heavy or light. . To
play, just select the problem type and number of coins and then
drag the coins to the balance s