You have ten coins, but two are fake, and weigh a little less. How many times do you have to use a two arm scale, in order to pick out the two fakes?

Supposing that there are ten of the exact same coins, the least number of times possible is 2 times.  Reasoning: suppose you are to get the two fakes on the first draw, they would weigh the exact same.  Next you draw a real coin that weighs more, rendering the balance uneven.  From this you are to gather that the first two were the fakes.  So there is no certain number of times until you're sure you have the fakes, but how quickly it is that you pick out the two fakes by accident/probability. 

Posted by David on 2005-03-28 05:33:41