Hongda Hotel currently has the lights on in 10 rooms. I flip the switches in 4 rooms at the same time each time. Can I turn off all the lights in these 10 rooms? How many times can I turn off the ligh

Hongda Hotel currently has the lights on in 10 rooms. I flip the switches in 4 rooms at the same time each time. Can I turn off all the lights in these 10 rooms? How many times can I turn off the lights?

It can be turned off and can be used at least three times.

The first time: 10-4=6; 10 rooms are closed and 4 rooms are left open;

The second time: 6-3+1= 4; Close 3 of the 6 open rooms, leaving 3 rooms open, and open 1 room that was closed for the first time at the same time, leaving 4 open at the same time;

< p>The third time: 4-4=0, the lights in all rooms are turned off.

Extended information:

To do one thing, there can be n types of methods to complete it. In the first type of method, there are m1 different methods, and in the second type of method, there are m2 different methods,..., there are mn different methods in the nth type of method, then there are N=m1+m2+m3+...+mn different methods to complete this thing.

The method of the first type of method belongs to the set A1, the method of the second type of method belongs to the set A2,..., the method of the nth type of method belongs to the set An, then the method to complete this thing belongs to the set A1UA2U …UAn.

Classification requirements: Each method in each category can independently complete this task; the specific methods in the two different categories are different from each other (that is, the classification is not overlapping); complete this task Any method belongs to a certain category (that is, the classification is not leaked).