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 7 sec. What is the length of the fast train? Choose the correct answer:
A) 38 7/6 m	B) 38 7/4 m	C) 38 8/9 m	D) 38 7/9 m	E) 38 7/7 m
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 * 7 = 350/9 = 38 8/9 m.Answer:38 8/9 m
<result>C</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 7 sec. What is the length of the fast train?