1, start time+time = end time

2. End Time-Start Time = Time

3. End Time-Time = Start Time

4. Work efficiency × working hours = total workload?

5. Total amount of work ÷ working hours = working efficiency?

6. Total amount of work ÷ work efficiency = working hours?

7. Number of tiles = room area/area of each tile.

8, the area of each floor tile = the area of the room, the number of floor tiles.

9. Room area = area of each floor tile × number of floor tiles.