Two trains of equal are running on parallel lines in the same direction at 42 km/hr and 36 km/hr. The faster train passes the slower train in 36 sec. The length of each train is?	Choices
A) 30 m
B) 72 m
C) 80 m
D) 82 m
E) 84 m

Rationale: "let the length of each train be x m . then , distance covered = 2 x m . relative speed = 42 - 36 = 6 km / hr . = 6 * 5 / 18 = 5 / 3 m / sec . 2 x / 36 = 5 / 3 = > x = 30 . answer : a"
Answer: A