Question { Sapient, 36163 }

You have 13 balls which all look identical. All the balls
are the same weight except for one. Using only a balance
scale, can find the odd one out with only 3 weighings?

Is it possible to always tell if the odd one out is heavier
or lighter than the other balls?

Answer

Devide these 13 balls into 3 categories i.e 6,6,1. Then measure both 6 and 6 . You will find the result. If both are equal then off one is the left out ball. If not equal then make another separate to the less weight 6 ball into 3 and 3. Same way measure these 3 and 3 . Find out the less weight side. Again separate this three into 1,1,1. Then measure any 2. You will find the needed result.