February 2011 Brain Teaser Solution

There are 8 similar balls. Seven of them weigh the same and the eighth is a bit heavier. How would you identify the heavier ball if you could use a two-pan balance scale only twice?

1. Put three balls on each side of the balance scale.  If they balance with one another, then all of these six are the same weight.
2. Take the last two balls and put them on the balance scale to find the heavier one.

OR


1. Put three balls on each side of the balance scale.  If they do not balance, take the three balls from the heavier side for the next step.

2. Pick two out of these three balls and put one on each side of the balance scale.  If they are different weights, you will find the heavier ball.  If they balance, then the heavier ball is the third ball.