You have ten boxes, each of which contains nine balls. The balls in one box each weigh 0.9 pounds; the balls in all the other boxes weigh exactly one pound each. You have an accurate scale in front of you, with which you can determine the exact weight, in pounds, of any given set of balls. How can you determine which of the ten boxes contains the lighter balls with only one weighing?

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You could probably feel which one is lighter without weighing it.

@BuddyCakes You could probably feel which one is lighter without weighing it.

I agree. But if you can't tell because of some defect in your ability to feel how heavy and object is... you could take one ball out of box 1, two balls out of box 2, 3 balls out of box 3, etc. weigh the remaining balls in the boxes (labeled properly) and tell that way. Of course the information would be of little value if you mix up the remaining balls, but the question is odd anyway why would you care which box contained the lighter balls - it seems like you should care which balls were lighter, not which box they were in - and why would you only be allowed one weighing? I mean the scale is right there, might as well use it.

Keep stacking the boxes one at a time while checking their weight after each box is added to the pile.

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