Problem-93

Problem-93

How many weighings of a balance scale are needed to find a lighter counterfeit coin among four coins? Which one of the following is the best algorithm to find the lighter coin?

 

Solution

At least 2 weighings are needed. We first compare the first two coins. If one is lighter, it is the counterfeit. If they balance, then we compare the other two coins, and the lighter one of these is the counterfeit.

 

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