Balance puzzle
A balance puzzle or weighing puzzle is a logic puzzle about balancing items—often coins—to determine which one has different weight than the rest, by using balance scales a limited number of times. The solution to the most common puzzle variants is summarized in the following table: For example, in detecting a dissimilar coin in three weighings ( n = 3 {\displaystyle n=3} ), the maximum number of coins that can be analyzed is 1 2 ( 3 3 − 1 ) = 13 {\displaystyle {\tfrac {1}{2}}(3^{3}-1)=13} .