A train moves past a telegraph post and a bridge 264 m long

A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train ?

Let the length of train be x metres.
Then, speed of train when it

passes a telegraph post =	x	m/sec.
	8

and speed of train, when it

passes the bridge =	x + 264
	20

Clearly,

x	=	x + 264
8	=	20

⇒	x	=	x + 264
	2		5

⇒ 5x = 2x + 528
⇒ 3x = 528

⇒ x =	528	= 176m
	3

∴ Speed of train =	176	= 22 m/sec.
	8

= 22 ×	18	Kmph
	5

= 79.2 kmph