A car travels along a certain road at an average speed of 60 kmph and returns along the same road at an average speed of 20 kmph.Calculate the average speed for the round trip.
A)20 kmph
B)30 kmph
C)40 kmph
D)50 kmph
E)60 kmph

Question

Quizplus · Accepted Answer

Let the distance travelled by the car be D.
Time taken to travel D at 60 kmph = D/60 hours
Time taken to travel D at 20 kmph = D/20 hours
Total time taken for round trip = D/60 + D/20 = (2D+6D)/120 = 4D/120 = D/30 hours
Total distance travelled in round trip = 2D
Average speed for round trip = Total distance travelled / Total time taken = (2D)/(D/30) = 60 kmph. 
Therefore, the correct option is (C).

A Car Travels Along a Certain Road at an Average