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?
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 be y m/sec
Then (x/y-5/9) = 9 and (x/y-10/9) = 10
therefore 9y - 5 = x and 10(9y - 10) = 9x
9y-x=5 and 90y-9x=100
on solving we get x=50
Then the length of the train be 50 metres.
Hope this information is helpful.