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Defective Balls

You have 10 boxes of balls (each ball weighing exactly10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?

SOLUTION : This puzzle is actually a simple one. Take 1 ball from box 1, 2 balls from box 2, 3 balls from box 3, and so on. Now, weigh all these 55 balls together. In an ideal scenario, the total weight that the machine should show is 550 gm. But, if box 1 has defective balls, it will show 1 gm less, if box 2 has defective balls, it will show 2 gms less , and so on. So, you can figure out the box with defective balls.

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