2012 ToT Fall Senior O p5 2 counterfeit coins among 239 identical coins
Source:
March 22, 2020
weighingscombinatorics
Problem Statement
Among coins identical in appearance there are two counterfeit coins. Both counterfeit coins have the same weight different from the weight of a genuine coin. Using a simple balance, determine in three weighings whether the counterfeit coin is heavier or lighter than the genuine coin. A simple balance shows if both sides are in equilibrium or left side is heavier or lighter. It is not required to find the counterfeit coins.