Jokes about functions

A scientist wanted to study the differences between people in different fields through experiments, so he hired an engineer, a physicist and a mathematician to paint the walls, but he didn't give enough paint. First, he went to see the engineer's results. The engineer's wall was partially painted and the paint was used up. The engineer said: I found that there was not enough paint, so I could only brush so much. Then he went to see a physicist. The physicist's wall has never been painted and the paint has never been touched. The experimenter asked what was going on, and the physicist said, I did some calculations before painting, and found that the paint could not be enough, so I simply stopped painting. Finally, the experimenter went to see the mathematician and was surprised to find that the mathematician's wall had been painted and there was no shortage of paint! The experimenter asked how this happened and how it was done. Mathematicians simply say: it's too simple. I painted rationality on the wall. The experimenter asked, "You lied to me. Rational points account for 0% of the wall area and have no color at all. " The mathematician said, well, I want to keep this secret. In fact, I divided the paint into five parts, and the two barrels of paint put together were as much as before.