A hotel with unlimited rooms, all rooms are full, and now there are 10000 people. How can these people stay in this hotel?

All passengers change rooms in turn according to the room number+10000, that is, the original room 1 0001,the original room 2 10002, and so on, vacant1-/.

In addition, it is also true for an infinite number of passengers. The original passengers all live in odd rooms, and new passengers can live in even rooms. Odd and even numbers are infinite. ....

Infinity plus infinity is still the original infinity, and only infinity multiplied by infinity is the higher infinity.

Where did this come from? . . There won't be such a wonderful problem before learning infinity, will there? There is no reason not to talk about learning infinite order. . . .