A two-pan scale does not give numbers: it only says left, right or balance. The challenge is to squeeze these three answers to locate one coin out of twelve and know if it weighs more or less.
The fake coin among twelve
Riddle statement
You have 12 seemingly identical coins. One of them is fake, and you don't know if it weighs more or less than the others. You have a two-pan scale.
What is the minimum number of weighings necessary to always identify the counterfeit coin and know if it is heavier or lighter?