A man is standing on a railway bridge which is 50 metres

A man is standing on a railway bridge which is 50 metres long. He finds that a train crosses the bridge
in 4 1 seconds but himself in 2 seconds.
2
Find the length of the train and its speed.

Let the length of the train be x metres
Then, the time taken by the train to cover (x + 50) metres is

4	1	seconds
	2

or	2x + 100	m per second ...(i)
	9

Again, the time taken by the train to cover x metres in 2 seconds.

∴ Speed of the train =	x	metre per second ...(ii)
	2

From equations (i) and (ii), we have

2x + 100	=	x
9	=	2

⇒ 4x + 200 = 9x
⇒ 5x = 200
⇒ x = 40
∴ Length of the train = 40 metres
∴ Speed of the train

=	x	=	40	= 20 m per sec.
	2		2

in 4	1	seconds but himself in 2 seconds.
	2