There are 12 balls in front of you. They are exactly the same size and shape, and there is no visible difference. However, one of the 12 balls has a different weight than the other 11, but is it heavier or lighter? we do not know. Our task is to find the ""problem ball"" using the only iso-arm balance at hand. But you only have three weighing opportunities at most. If you need the fourth (and above) weighing to find the ""problem ball"", you lose. Okay, fasten your seat belts, we're ready to start the challenge!