Excluding stoppages, the average speed of a bus is 60 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?	Options
A) 20 min
B) 30 min
C) 40 min
D) 35 min
E) 37 min
A   20 min   In 1hr, the bus covers 60 km without stoppages and 40 km with stoppages.   Stoppage time = time take to travel (60 - 40) km i.e 20 km at 60 km/hr.   stoppage time = 20/60 hrs = 20 min.
<result>A</result>
Excluding stoppages, the average speed of a bus is 60 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?