Two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the faster train in 8 seconds. The length of the faster train is

A.   80 m   
B.   100 m
C.   120 m   
D.   180 m
Answer: D

Explanation:

Relative speed    = (36 + 45) km/hr
                          = (81 x 5/18) m/sec
                          = (45 / 2) m/sec
Length of the train = (45 / 2 x 8) m
                            = 180 m.