The general counterfeit coin problem Original Research Article

Given c nickels among which there may be a counterfeit coin, which can only be told apart by its weight being different from the others, and moreover b balances, what is the minimal number of weighings to decide whether there is a counterfeit nickel, if so which one it is and whether it is heavier or lighter than a genuine nickel. We give an answer to this question for sequential and nonsequential strategies and we will consider the problem of more than one counterfeit coin.