Question

A train traveling at a uniform speed passes by a platform 220 m long in 30 s and another platform 325 m long in 39 s Find.
(i) the length of train and the speed of train​

Answer 1

Step-by-step explanation:

Let the speed of the train be x m/sec and length of the train be y m. Then,

Speed of the train

Length of the train

= Time taken by the train to pass the man

⇒

x

y

=15⇒y=15x ......... (1)

and

Speed of train

Length of train + Length of platform

= Time taken by the train to cross the platform

⇒

x

y+90

=30⇒y+90=30x ........ (2)

Put the value of y from (1) in (2)

15x+90=30x⇒15x=90⇒x=6m/sec

∴ Speed of train =(6×

5

18

)km/hr=21.6km/hr.

Answer 2

Given s =t+ 220/30 ••••••• (1)

and s= t + 325/39 ••••••• (2)

on solving (1) and (2), we get

39(t + 220) = 30(t + 325)

39t + 8580 = 30t + 9750

9t = 1170

t = 130 metres

Substitute in (1), we get

Speed = 130 + 220/30

= 350/30 =

= 11.66 m/sec

On converting it to km/hr, we get

S = 3600 * 11.66/1000

= 41.9

= ~42