How would you figure out which of 9 pennies is heaviest in only 2 weighings when only 1 penny is heavier than the others?

The two pennies being chosen from the remaining three are weighed against each other. If one is heavy there it is, if they are equal the left over penny is it. Hope this helps. There are ONLY two measurements being used. The first with the two sets of three, the final with one on one from a set of three.

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