Two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the faster train in 6 seconds. The length of the faster train is	Choose the correct choice from the following answers: A) 80 m B) 100 m C) 120 m D) 135 m E) none

Rationale: "solution relative speed = ( 36 + 45 ) km / hr = ( 81 x 5 / 18 ) m / sec = ( 45 / 2 ) m / sec length of the train = ( 45 / 2 x 6 ) m = 135 m . answer d"
Answer: D