Distance between two stations A and B is 1108 km. A train covers the journey from A to B at 84 km per hour and returns back to A with a uniform speed of 56km per hour. Find the average speed of train during the whole journey. Answers:	A) 60 km/hr	B) 30.5 km/hr	C) 57 km/hr	D) 67.2 km/hr	E) None of these
Explanation :   Average speed = (2xy)/(x+y) km/hr   = (28456)/(84+56) km/hr   = (28456)/140 km/hr   = 67.2 km/hr.   Answer : 67.2 km/hr
<result>D</result>
Distance between two stations A and B is 1108 km. A train covers the journey from A to B at 84 km per hour and returns back to A with a uniform speed of 56km per hour. Find the average speed of train during the whole journey.