A 120 metres long train is running at a speed of 90 km per hour. It will cross a railway platform 230 m long in ?

Answer: Option D

Here, speed of the running train is 90 km/hr
And length of the train is = 120 metres
We know that,
When a train crosses through the platform, it cover the distance equal to the length of platform + length of the train
So, the time will taken by the train :

$$\frac{\text{Length of train}+\text{Length of platform}}{\text{Speed}}$$
$$\begin{array}{rl}& =\frac{\left(120+230\right)\text{ metres}}{90\text{ km/hr}}\\ & =\frac{350\times 18}{90\times 5}\\ & =14\sec \end{array}$$