MathDB

8.8

Part of 2006 All-Russian Olympiad Regional Round

Problems(1)

N coins - All-Russian MO 2006 Regional (R4) 8.8

Source:

9/27/2024
When making a batch of N≥5N \ge 5 coins, a worker mistakenly made two coins from a different material (all coins look the same). The boss knows that there are exactly two such coins, that they weigh the same, but differ in weight from the others. The employee knows what coins these are and that they are lighter than others. He needs, after carrying out two weighings on cup scales without weights, to convince his boss that the coins are counterfeit easier than real ones, and in which coins are counterfeit. Can he do it?
combinatoricsweighings