There are 12 coins, and only one coin has different weight (unknown weight). Use an uncalibrated balance to find coins through three balances. Solution?

Solution: One of the three animals moved from the original left disk to the right disk is fake and very light. Next, put any two of these three into the left and right plates and weigh them for the third time. If they are unbalanced, the rising side will be false. If it is balanced, the rest are false.

If the left disk is raised (it can also be lowered, the method is similar, and the results are clear), which means that the four unverified ones are true. Three are randomly selected from the left disk to replace three in the right disk, and three are selected from the unweighted ones to supplement the left disk.

Notes on mathematical logic:

Psychologists have found through systematic research that the effect of intentional memory is much better than that of unintentional memory. Therefore, maintaining a high degree of concentration is essential for maintaining rational and calm logic and for analyzing and solving problems.

In order to maintain a high degree of concentration, we need to pay attention to the stability, persistence and easy concentration.