Excluding stoppages, the average speed of a bus is 80 km/hr and including stoppages, the average speed of the bus is 40 km/hr. For how many minutes does the bus stop per hour?  Choose the correct choice from the following answers:
A) 15 min B) 18 min C) 16 min D) 20 min E) 30 min
In 1hr, the bus covers 80 km without stoppages and 40 km with stoppages.   Stoppage time = time take to travel (80 - 40) km i.e 40 km at 80 km/hr.   stoppage time = 40/80 hrs   = 30 min   Answer: 30 min
<result>E</result>
Excluding stoppages, the average speed of a bus is 80 km/hr and including stoppages, the average speed of the bus is 40 km/hr. For how many minutes does the bus stop per hour?