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.