MathDB

M2730

Part of Kvant 2023

Problems(1)

Counterfeit coins

Source: Kvant Magazine No. 1 2023 M2730

3/7/2023
On each cell of a 3×63\times 6 the board lies one coin. It is known that some two coins lying on adjacent cells are fake. They have the same weigh, but are lighter than the real ones. All the other coins are real. How can one find both counterfeit coins in three weightings on a double-pan balance, without using weights?
Proposed by K. Knop
Kvantcombinatorics