Marbles Solution

For the first time using the scale take six marbles and place three on each side. The side that is heavier will drop. Take the three marbles from the side that has dropped and put one of them on each side, leaving one out for the second scale usage. The side that falls now is the heavier one. If the scale is equal the second time then the one you left out is the heavier one. If the scale is equal right after the first scale usage, then you know the heavier one is in the three marbles not initially scaled and you just treat these three like before leaving one out and weighing the other two.

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