Distance between two stations A and B is 778 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 56 km perhour. Find the average speed of the train during the whole journey.
Options:
A . 67.1
B . 67.2
C . 67.4
D . 67.3
Answer: Option B
Required average speed = ((2xy)/(x+y)) km / hr =(2 x 84 x 56)/(84+56)km/hr =(2*84*56)/140 km/hr =67.2 km/hr.
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