Excluding stoppages, the average speed of a bus is 54 kmph and including stoppages, it is 45 kmph. For how many minutes does the bus stop per hour?

A. 9
B. 10
C. 12
D. 20

Due to stoppages, the bus travels only 45 kms in an hour (9 kms less). To cover a distance of 9 km at a speed of 54 kmph, time taken
= 9/54 = 1/6 hrs = 10 mins.