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10.2

Part of 2000 All-Russian Olympiad Regional Round

Problems(1)

5 coins, 2 fake - All-Russian MO 2000 Regional (R4) 10.2

Source:

9/26/2024
Among five outwardly identical coins, 33 are real and two are fake, identical in weight, but it is unknown whether they are heavier or lighter than the real ones. How to find at least one real coin in the least number of weighings?
combinatoricsweighings