Riddle: You are given 9 steel balls and a scale (like the Libra sign)and a puzzle to solve. One of these 9 balls is very light and needs to be replaced. You can only use the scales twice and you must find the light ball. How will you do this?
Answer: *1.)First you put 3 balls on each side and three in your hand (3+3+3=9). If they weigh the same, the light ball is not there. If the do not weigh the same then the lighter side will contain the light ball.
Either way that will leave ONLY three balls to choose from (the three in your hand or the three on the scale). *2.)Of the 3 balls put one on each side of the scales.....and if one side is lighter you have it! If they weigh the same, we know the one is your hand is the light ball.