This sentence comes from the statue of Cao Chong in the History of the Three Kingdoms in the Eastern Han Dynasty.
Cao Chong is an elephant.
Original text:
Cao Chongsheng was only five or six years old, and he had the wisdom of an adult. At that time, Sun Quan once gave birth to a giant elephant, and Mao wanted to know its weight. It is impossible to be reasonable under the group he visited. Chong said, "Put it on a big ship, carve its water mark, weigh it, transport it, and you will know." Mao said, that is, how to implement it.
Translation:
When Cao Chong was five or six years old, he was as knowledgeable and judgmental as an adult. Once, Sun Quan sent a giant elephant. Cao Cao wanted to know the weight of the elephant, so he asked his men, but they didn't know how to weigh it. Cao Chong said: "Put the elephant on the big ship, mark where it reaches the water surface, and then let the ship carry other things, weigh them and compare them." Cao Cao was very happy and did it at once.
Extended data:
In fact, the clever Cao Chong used the method of "equal replacement". Replace the elephant with many stones, mark the boat, make the elephant and the stone have the same effect, weigh the stones repeatedly, turn "big" into "small", divide and conquer, and this problem will be solved satisfactorily.
Equivalent substitution method is a common scientific thinking method. Here is a short story about Edison. The great American inventor Edison had an assistant named Aptom, who had a good foundation in mathematics. Once, Edison gave Aptom the glass shell of a light bulb and asked him to calculate the volume of the light bulb.
Aptom looked at the pear-shaped bulb shell, thought for a long time, drew the sectional view and perspective view of the bulb shell, drew a series of complicated curves, measured the data one by one, and listed a series of formulas. After several hours of intense calculation, the result hasn't come out yet. Edison was very dissatisfied after reading it.
I saw Edison fill the bulb shell with water and then pour the water into the measuring cup. In less than a minute, he calculated the volume of the light bulb. Here, Edison replaced the volume of the bulb shell with the volume of water poured into the measuring cup, and also used the equivalent replacement method.