Excluding stoppages, the average speed of a bus is 60 km/hr and including stoppages, the average speed of the bus is 20 km/hr. For how many minutes does the bus stop per hour? Choose the correct choice from the following
A) 22  B) 88  C) 77  D) 40  E) 99

Rationale: "in 1 hr , the bus covers 60 km without stoppages and 20 km with stoppages . stoppage time = time take to travel ( 60 - 20 ) km i . e 40 km at 60 km / hr . stoppage time = 40 / 60 hrs = 40 min . answer : d"
Answer: D