A person travels 20 km at 12 km/h and the next 35 km at 20 km/h. What is his…

Solution: Find the average speed by dividing total distance by total time.

1. Total distance = 20 km + 35 km = 55 km.

2. Time for first part = distance/speed = 20/12 = 5/3 hours ≈ 1.6667 hours.

3. Time for second part = 35/20 = 7/4 hours = 1.75 hours.

4. Total time = 5/3 + 7/4 = (20 + 21)/12 = 41/12 hours ≈ 3.4167 hours.

5. Average speed = total distance ÷ total time = 55 ÷ (41/12) = 660/41 ≈ 16.1 km/h.

Answer: 16.1 km/h

Note: Do not use a simple arithmetic mean of the two speeds; the correct approach is total distance divided by total time.