A car covers 100 km at 60 km per hour and returns 100 km at 40 km per hour. The average speed is

Average speed is total distance divided by total time. The distance is 200 km. The time for first part is 100 ÷ 60 hours which is 5/3. The time for second part is 100 ÷ 40 hours which is 5/2. Total time is 25/6 hours. Average speed = 200 ÷ (25/6) = 48 km/h. This formula is important for solving problems with different speeds in both directions.