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 5 sec. What is the length of the fast train?
Pick one:
A) 27 7/8
B) 27 7/6
C) 27 7/4
D) 27 7/9
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 * 5 = 250/9 = 27 7/9 m.   Answer: 27 7/9
<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 5 sec. What is the length of the fast train?