Question

A car travels from A to B, which are 120 km apart, at a constant speed in 4 hours. It comes back to A in 2 hours, moving the first hour at 90 km/h and the rest of the journey at 30 km/h. Calculate the average speed of the car during the journey.

• A. 45 km/h
• B. 40 km/h
• C. 30 km/h
• D. 60 km/h

Answer 1

The correct option is B 40 km/h

Distance travelled from A to B = 120 km
Time taken during the journey = 4 h

On the return journey,
Distance travelled from B to A = 120 km (90 km in the first hour at 90 km/h + 30 km in the second hour at 30 km/h)

Time taken during the journey = 2 h
Average speed is the total distance covered divided by the total time taken.
$v_{av}=\frac{120+120}{4+2}=40km/h$