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There are pan scales without weights and 3 visually identical coins, one of which is counterfeit: it is lighter than the genuine ones (the genuine coins weigh the same). How many weighings are needed to determine the counterfeit coin?

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When searching for a counterfeit coin among three coins, try placing one coin on each pan of the balance.

## Solution

We will need only 1 weighing. Place one coin on each pan of the balance. If one of the pans is lighter, the counterfeit coin is on it. If the balance is even, the counterfeit coin is the one that was not placed on the balance.