A motorist travels to a place 150 km away at an average speed of 50 km/hour and returns at a speed of 30km/hour. His average speed for the whole journey is
1
35 km/hour
2
37.5 km/hour
3
40 km/hour
4
42.5 km/hour
A motorist travels to a place 150 km away at an average speed of 50 km/hour and returns at a speed of 30km/hour. His average speed for the whole journey is