Multiple choice

A train is running at a speed of 36 km/hr. It crosses a railway platform in 20 seconds and a boy standing on the platform in 10 seconds. Find the length of the platform.

  1. 200 m

  2. 100 m

  3. 50 m

  4. 240 m

  5. 120 m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The train speed is 36 km/hr, which is 10 m/s. The length of the train is the distance covered in 10 seconds (passing a boy), so 10 m/s * 10 s = 100 m. The train covers the platform length plus its own length in 20 seconds, so 10 m/s * 20 s = 200 m; subtracting the train length gives 200 - 100 = 100 m.

AI explanation

First, convert the train's speed of 36 km/hr to meters per second by multiplying by 5/18, which gives a speed of 10 m/s. Since the train takes 10 seconds to cross the boy standing still, its length is 10 m/s multiplied by 10 s, resulting in 100 m. When crossing the 20-second platform, the total distance covered is 10 m/s multiplied by 20 s, equaling 200 m. The platform length is the total distance minus the train's length: 200 - 100 equals 100 m.

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