Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is:  Choose the correct option
A) 50 m B) 72 m C) 80 m D) 82 m E) 92 m

Rationale: "let the length of each train be x metres . then , distance covered = 2 x metres . relative speed = ( 46 - 36 ) km / hr = ( 10 x ( 5 / 18 ) m / sec = ( 25 / 9 ) m / sec ( 2 x / 36 ) = ( 25 / 9 ) 2 x = 100 x = 50 . a"
Answer: A