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There are 9 identical balls but only one of them has a higher weight. You are also given a weight balance. How many attempts would you require to identify the ball with the extra weight and how?


marked as duplicate by IAmInPLS, Gamow, elias, Marius, Beastly Gerbil Aug 25 '16 at 11:30

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Classic puzzle, you need


You do this by

Measuring a set of three versus a set of three. The set with the heavy ball is identified. (The heavier set on the scale, or, if they are equal, the set not on the scale)

Weigh two of the balls in said set of three, same thought process. Heavier on the scale, or the one left over if they are the same.


I think

2 steps.


Divide the balls into three gropus of three. Weigh two groups first. Now weigh any two balls of the heavier group (if both the groupare of same weight, the third group). You will know which one is the heavier ball.


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