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The Counterfeit Coin

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Author:Ivars Peterson (MathTrek)
Description: The classic puzzle of the counterfeit coin has long served as a stiff test of one's reasoning power and ingenuity. In its standard form, the problem concerns 12 coins identical in size, shape, and appearance. One coin, however, is counterfeit, having a slightly different weight than the other 11 coins. Using only a two-pan balance, what is the smallest number of weighings that would guarantee that you would find the counterfeit coin?

Levels: Middle School (6-8), High School (9-12), College
Languages: English
Resource Types: Problems/Puzzles, Articles
Math Topics: Algorithms, Logic/Foundations

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