Explanation:

The train crosses the pole in 9 seconds meaning that it travels its length in these 9 seconds. Therefore the distance travelled by the train is the length of the train. Convert the given velocity to m/s or the time to hours for correct calculation.

1 km = 1000 m . 1 hr = 3600s

Velocity = 60 × 1000 / 3600 = 50/3 m/s .

Now distance = velocity × time

= 50 / 3 × 9 = 50 × 3 = 150 m

Therefore the length of the train is 150 metres.

Hence, option 3 is the correct answer.