A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. Find the length of train ? Answers:
A) 45 m B) 50 m C) 55 m D) 60 m E) 65 m

Rationale: "explanation : first person speed = 2 * ( 5 / 18 ) = 5 / 9 m / sec second person speed = 4 * ( 5 / 18 ) = 10 / 9 m / sec let the length of train is x metre and speed is y m / sec then , x / y − 5 / 9 = 9 = > 9 y − 5 = x = > 9 y − x = 5 . . . . . ( i ) also , x / y − 10 / 9 = 10 90 y − 9 x = 100 . . . . . ( ii ) from ( i ) and ( ii ) , we get , x = 50 so length of train is 50 metre option b"
Answer: B