A train passes a 50 metres long platform in 14 seconds and a man standing on the platform in 10 seconds. The speed of the train is:

Let the length of train be L m.

$$\frac{L}{10} = \frac{L + 50}{14}$$

14L = 10L + 500

L = 125 m.

$$Speed = \left ( \frac{25}{2} \right )$$ m/s

= $$\left ( \frac{25}{2} \right ) \times \frac{18}{5}$$

= 45 km/hr