This is a magical topic. If you think according to his ideas, you will only feel confused, but if you touch your own ideas a little, you will find the mystery. First of all, the 9 yuan money spent by each person already includes the 2 yuan hidden by the waiter (that is, the preferential price of 25 yuan+the waiter's possession of 2 yuan =27 yuan =3*9 yuan). Therefore, when calculating the composition of 30 yuan, the 2 yuan money hidden by the waiter cannot be counted, but should be added with 1 yuan returned to everyone. That is: 3*9+3* 1=30 yuan happens to be: (1) three scholars live in an inn, and the result is 10 yuan per person, * * 10 × 3 = 30 yuan. (2) Each person returned 1 yuan, that is, each person spent 9 yuan money and three people spent 27 yuan money. Of the 27 yuan, the boss kept 25 yuan and the second kept 2 yuan privately. (3) Add the returned 3 yuan money, and the result happens to be 30 yuan. Conclusion: This puzzle is mainly because it separates 2 yuan from 27 yuan. The original algorithm mistakenly thought that the 2 yuan money left by Xiao Er was not. In fact, this 27 yuan includes 2 yuan left privately. Add the returned 3 yuan money, and the result happens to be 30 yuan.

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