Question

A bus maintains an average speed of 60 km/hr while going from P to Q and maintains an average speed of 90 km/hr while coming back from Q to P. The average speed of the bus is ....

(A) 75 km/hr

(B) 72 km/hr

(C) 70 km/hr

(D) 30 km/hr

Answer 1

The correct option is: (B) 72 km/hr

Explanation:

Average speed = Total distance covered/Total time taken

Let x be the distance between P and Q.

Thus, time taken by bus from P to O (t₁) = x/60

Time taken by bus from O to P (t₂) = x/90

Total distance covered = 2x 

and total time taken = t₁ + t₂