Puzzles & Tricks: Twelve Coins Puzzle
Twelve Coins Puzzle
In this video, we present a classic puzzle that challenges people to think in an unconventional manner. Like many of the best puzzles, this problem is easy to understand, but difficult to solve.
We begin with twelve identical coins, one of which is counterfeit. The counterfeit looks exactly like the others, but it is either heavier or lighter than the other coins.
The problem is to find the counterfeit coin, and determine whether it is lighter or heavier than the others. This must be done with no more than three weighings of a pan balance.
A pan balance is a simple scale that can be used to determine if one object is lighter than the other, but it cannot be used to calculate weight directly. Here is the solution.