Another variation was presented in my psych class. There are eight coins of unknown weight each. Using a scale twice, identify which one is the false coin. The

Another variation was presented in my psych class. There are eight coins of unknown weight each. Using a scale twice, identify which one is the false coin. The false coin is lighter than the regular coins, which are all of the same weight. I found this one less intuitive; if you use the same algorithm as the 12 balls problem, it requires using the scale three times, which is one over the amount of times you're allowed to use the scale.