wtm@ihuxb.UUCP (Bill Matern) (05/30/84)
>You are given 12 coins and a balance. Eleven of them are the same >weight. The other coin is either heavier or lighter. Your mission, >should you choose to accept it, is to discover which coin it is that >has the non-standard weight, and whether it is heavier or lighter than >the standard weight. You can use the balance for comparing the weights >of two different groups of coins. You must accomplish this with three >weighings or less. Can you do it for 13 coins in which one is either heavier or lighter if a 14th ball known to be good is provided???
4341fah@houxn.UUCP (05/31/84)
you can find the bad (heavier or lighter) coin of thirteen with three weighings without a fourteenth "good" coin - after one weighing you know where at least 4 "good" coins are. The only hitch here is that for 1 of the 13 cases you won't know if the "bad" coin is heavier or lighter after 3 weighings - only that it's "bad"! Fred Hicinbothem