A train 180 m long is running at a speed of 90 km/h. How long will it take to pass a post?

Correct option is C

Given:

Length of the train (distance) = 180 meters

Speed of the train = 90 km/h

Formula Used:

$$\text{Time} = \frac{\text{Distance}}{\text{Speed}}$$​

Solution:

Speed of the train = 90 km/h

$$\text{Speed in m/s} = 90 \times \frac{5}{18} = 25 \, \text{m/s}$$

Now:

​$$\text{Time} = \frac{\text{Distance}}{\text{Speed}} = \frac{180 \, \text{m}}{25 \, \text{m/s}} = 7.2 \, \text{seconds}$$

It will take the train 7.2 seconds to pass a post.​​