Question

A train crosses a 200 m tall lamp post in 10 seconds and a 300m long platform in 20 seconds. Find the length of the train in meters.

• A. 100 m/s
• B. 150 m/s
• C. 250 m/s
• D. 300 m/s

Answer 1

The correct option is D 300 m/s

In the first case, the height of the lamp post is immaterial.

Also, the train crosses the lamp post in 10 seconds and then it crosses its own length in 10 seconds.

In the extra (20 – 10) = 10 seconds in the next case, the train crosses the 300 m long platform.

So, the speed of the train = 300/10 = 30 m/s

Now, it took 10 seconds to cross the lamp post, that is, its own length.

So, length = 30 × 10 m = 300 m

Hence, option (D) is the correct answer.