Subject: Brain Teaser Answer
Date: Thu, Aug 17 2000 00:00:02 EDT

Answer to Brain Teaser

First, divide the coins into three groups of three.

Then, balance any one group against another group.

If the counterfeit coin is contained in either of the groups, the coins will not balance. If, however, they balance, the counterfeit coin must be in the third pile.

Now that we have identified the group with the counterfeit coin, remove one coin from that group, and balance the other two.

The lighter coin will not balance. If they do balance, the counterfeit coin is the one not selected.