Two trains of equal are running on parallel lines in the same direction at 45 km/hr and 36 km/hr. The faster train passes the slower train in 36 sec. The length of each train is?  Pick.
A) 45  B) 88  C) 66  D) 55  E) 22

Rationale: "let the length of each train be x m . then , distance covered = 2 x m . relative speed = 45 - 36 = 9 km / hr . = 9 * 5 / 18 = 5 / 2 m / sec . 2 x / 36 = 5 / 2 = > x = 45 . answer : a"
Answer: A