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. The length of the train is: Choose the correct option.
A) 10	B) 100	C) 50	D) 200	E) 300
2 kmph =	(2 x	5/18	)m/sec =	5/9	m/sec.   4 kmph =	(4 x	5/18	)m/sec =	10/9	m/sec.   Let the length of the train be x metres and its speed by y m/sec.   Then,(x/y -5/9)= 9 and(x/y -10/9)= 10.   9y - 5 = x and 10(9y - 10) = 9x   =&gt; 9y - x = 5 and 90y - 9x = 100.   On solving, we get: x = 50.   Therefore Length of the train is 50 m.   Answer: 50
<result>C</result>
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. The length of the train is: