Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 8 sec. What is the length of the fast train?  Select.
A) 27 7/6 B) 277/5 C) 27 7/2 D) 400/9 E) 27 7/1
Relative speed = (40 - 20)= 
<gadget id="calculator">(40 - 20)</gadget>
<output>20</output>
20 km/hr.= 20 * 5/ 18 = 50/9 m/sec.   Length of faster train = 50/9 * 8 = 400/9   = 27 7/9 m.   Answer:400/9
<result>D</result>
Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 8 sec. What is the length of the fast train?