Question

a train travelling at a uniform speed passes by a platform 220 M long in 30 seconds and another platform 325 M long in 39 seconds find the length of the train and the speed of the train

Answer 1

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

Answer 2

L of platform =220m

30sec=220m

39sec=325m

Subtract 325and220=105

S=10/9=35/3

35/3*18/5=42km/hr