Three people stay.

The waiter said 30 yuan.

Everyone handed in 10 yuan.

Make up for 30 yuan.

Later, the boss said it was on sale today.

As long as 25 yuan.

So I asked the waiter to refund them, 5 yuan.

The waiter has to hide 2 yuan for himself.

Just give them 3 yuan.

Three people each took 1 yuan.

10-9 = 1 means to pay only the accommodation fee in 9 yuan.

9*3 2 yuan+waiter = 29 yuan

What about the remaining 1 yuan?

This kind of topic is very interesting, and it is also the interest of mathematics! In fact, the problem is that "three people each got 1 yuan, 10-9 = 1, which means they only paid the accommodation fee in 9 yuan". The mistake is that when the boss made a special offer, everyone paid 8 1/3 yuan instead of 8 yuan, so after returning 1 yuan, everyone's 1/3 yuan will be discarded according to the algorithm in the topic, which is incorrect. The reason for this problem is that we all know that 1/3x3= 1, 1/3 is equal to 0.33333 ... infinite loop, 0.33333...× 3 = 0.999999 ... infinite loop, not equal to 65438+. At this time, the problem of 1 yuan seems clear!

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