Two trains are running at 40 km/hr and 20 km/hr respectively in teh same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?  Pick one: A) 27 7/9 m B) 28 m C) 29 D) 30 E) None
Sol.   Relative speed = (40-20) km/hr = [20 * 5/18] m/sec = [50/9] m/sec.   Length of faster train = [50/9 * 5] m = 250/9 m = 27 7/9 m.   27 7/9 mnswer 27 7/9 m
<result>A</result>
Two trains are running at 40 km/hr and 20 km/hr respectively in teh same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?