This puzzle is similar to the Defective balls asked by microsoft. In this case instead of 10 balls here 12 balls. The puzzle question and answers are given below.

Defective balls
Puzzle Question :

          You have 12 identical balls. One of the balls is heavier OR lighter than the rest (you don't know which). Using just a balance that can only show you which side of the tray is heavier, how can you determine which ball is the defective, how many measurements required??

Answer :

         comment your answers...