A bus runs at 54 km/h excluding stoppages and 45 km/h including stoppages. How many minutes does it stop per hour?

Including stoppages reduces the effective hourly distance. The ratio of effective to running speed gives the fraction of time spent moving.

Step-by-step calculation
Running speed (no stops) = 54 km/h ⇒ covers 54 km in 1 h while movingEffective speed (with stops) = 45 km/h ⇒ covers 45 km in the whole hourFraction of hour spent moving = 45 / 54 = 5/6Stoppage fraction = 1 − 5/6 = 1/6 of an hourStoppage time per hour = (1/6) × 60 = 10 minutes

Final Answer
10 minutes