Content of this book: The law of exchange is as useful in arithmetic as in daily life. However, you can't use it indiscriminately. The story of monkeys eating chestnuts is of course made up by people, but it is not true. However, the breeder who feeds the game knows; Feed the pig with coarse grains first, and then add refined feed, so that it can eat well, sleep well and grow fast. The exchange method is not applicable here. There are some things, and their order is not interchangeable. Wear socks first, then shoes. That's right. On the contrary, wear shoes first, then socks. What else would it look like? Unscrew the pen cap, fill it with ink, and then write. That's right. On the other hand, it is impossible. ……

Monkeys divide peaches.

There are many peaches here. This is the public property of five monkeys. They should divide it equally.

Here comes the first monkey. It waited left and right, and when the other monkeys didn't come, it began to divide the peaches into five piles, leaving 1. He felt that he had worked hard and deserved to eat this 1 unallocated peach and took five piles of 1.

Here comes the second monkey. It doesn't know what just happened. It divided the peaches into five piles, or there were more 1.

It ate 1 and took the pile of 1. After that, every monkey came, and that's it.