Excluding the stoppages, the speed of a bus is 12 km/hr and including the stoppages the speed of the bus is 6 km/hr. For how many minutes does the bus stop per hour?  Answers:	A) 15 min	B) 30 min	C) 12 min	D) 20 min	E) 18 min

Rationale: "speed of the bus without stoppage = 12 km / hr speed of the bus with stoppage = 6 km / hr difference in speed = 6 km / hr so , the time taken in the stoppages = time taken to cover 6 km = ( 6 / 12 ) hr = 1 / 2 hr = 30 min answer : b"
Answer: B