Academician Mathematics Lecture Album -- Help You Learn Mathematics (Latest Version)

Author: Zhang Jingzhong
Publisher:
Publish Date: 2004-04-01
Features: The commutative law in arithmetic is just as useful in daily life. However, you can't use it recklessly either. The story of monkeys eating chestnuts is, of course, made up by people and not a factual account. But the zookeeper who feeds the animals knows that when feeding pigs, one should first give them roughage and then add fine feed to make the meal more appealing, so they can eat well, sleep soundly, and grow faster. The commutative law doesn't hold here. There are also some things where the order is fundamentally unchangeable. Putting on socks before shoes is correct. But what if you put on shoes before socks? It just doesn't make sense. Unscrew the pen cap, fill it with ink, and then write—this is correct. But the reverse is impossible. The commutative law in arithmetic is just as useful in daily life. However, you can't use it recklessly either. The story of monkeys eating chestnuts is, of course, made up by people and not a factual account. But the zookeeper who feeds the animals knows that when feeding pigs, one should first give them roughage and then add fine feed to make the meal more appealing, so they can eat well, sleep soundly, and grow faster. The commutative law doesn't hold here. There are also some things where the order is fundamentally unchangeable. Putting on socks before shoes is correct. But what if you put on shoes before socks? It just doesn't make sense. Unscrew the pen cap, fill it with ink, and then write—this is correct. But the reverse is impossible.