V 1+V2=28

5V 1-V2=56 (28 and 56 here are regarded as an abstract journey. )

You can get v1=14v2 =14, so Xiao Ming's speed is the same as that of the elevator.

It can be concluded that the time for Xiao Ming to go down the stairs is half the speed of the elevator (S/2V2).

So S/2=28, and the whole staircase tree is 56.

2. Let x be the original number of stairs with 4 to 5 floors, and Y be the reduced number of stairs.

X+(X-Y)+(X-2Y)=45

X-Y= 15。

So the number of stairs on floors 5 to 6 is 15 and.

Because each floor decreases in turn, the real Y added to the fifth floor from 1 and the Y reduced from 6 to 10 can be offset, so the stairs and trees of the tower are 15*9= 135 and.

3. let the time be t and the number of stairs be s.

4T=S

3(T+4)=S

You can get T= 12 S=48.

So the number of stairs is 48.

4. The speed of A going upstairs is 18/2=9S, and the speed of B going downstairs is 18/3=6S.

So A should go upstairs from the 6th floor, and B should go downstairs from the 9th floor. This building has 6+(6*9)/9= 12 floors.

5. 1 on the hour

0 hours later, 6.65438+6 minutes

Is your question about grade one? Oh, the knowledge of senior one is so abnormal now?