I was reminded of a good puzzle I solved a long, long time ago in HS. Let's see whom here can solve it.
You have 12 balls numbered 1-12 that otherwise appear and feel identical, except one is either slightly heavier or lighter than the other 11 (you can't feel it). Using only a balance scale w/o weights, how do you identify the odd ball and whether it is heavier or lighter than the others with only 3 weighings on the scale?