A * * * has three layers. From the first floor to the fourth floor, take three floors: the first to the second floor, the second to the third floor, and the third to the fourth floor.

In mathematics, the hierarchical problems encountered when climbing stairs are mainly understood as different floors and stairs. From the bottom, the number of floors is more than the number of stairs 1, that is, the number of floors = the number of stairs+1, and the number of stairs = the number of floors-1.

Other similar questions:

It takes Xiaoming 2 minutes to climb a floor. How many minutes does it take to get from the first floor to the fourth floor? Or Xiaoming takes 2 minutes to climb the first floor and 8 minutes to climb the stairs after school. What floor does Xiaoming's family live on?

The first question: how many floors have you climbed = the floor where you live-1, so the first question is like this: 2×(4- 1)=6.

The second question: the floor where you live = the number of floors you climb+1, so the second way is calculated as follows: 8÷2+ 1=5.