A motorist travels to a place 150 km away at an average speed of 50 km and returns at 30 km per hour. What is his average speed for the whole journey in km per hour?

A 35

B 37

C 37.5

D 40

Correct Answer: Option C

We know that, Speed = Distance/Time taken

Thus, Time taken = Distance/Speed

While Travelling,

Time taken = 150/50 = 3 hours

While Returning,

Time taken = 150/30 = 5 hours

Total time taken during the journey = 3 + 5 hours = 8 hours

And, Total distance covered during the journey

= (150 + 150) km

= 300 km

Thus Speed = 300/8 = 37.5 km/h