Trains Q4

4.A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:

     A.   50 m

     B.   150 m

     C.   200 m

     D.   Data inadequate

Option : B 

Let the length of the train be X metres and its speed by Y m/sec.

Then,	X	= 15
	18

⇒ Y =	X
	Y

∴	X + 100	=	X
	25		15

⇒ 15(X + 100) = 25X

⇒ 15X + 1500 = 25X

⇒ 1500 = 10X

⇒ X = 150 m.