A train overtakes two person 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. The length of the train is: Pick:	A) 45 m	B) 50 m	C) 54 m	D) 72 m	E) none of these

Rationale: let actual speed of train = s m / sec and length of train = l m . then , s - 2 × 5 / 18 = l 9 ⇒ 9 s = l + 5 . . . … ( i ) and s - 4 × 5 ⁄ 18 = l ⁄ 10 ⇒ 90 s = 9 l + 100 . . . . . ( ii ) by ( i ) & ( ii ) , we get l = 50 m . answer b
Answer: B