Multiple choice

The numericle value of the speed of a train in km/hr is double of the time taken by it to cross a platform while it crosses a platform in 30 seconds. If the length of the train be 200 metres, then the length ( in metres) of the platform is

  1. 400

  2. 300

  3. 200

  4. 500
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given speed (numerical value) = 2 × time (seconds). Let speed = v km/hr and time = 30 seconds. Since v = 2 × 30, we get v = 60 km/hr = 60 × (5/18) = 50/3 m/s. Distance in 30 seconds = (50/3) × 30 = 500 m. This distance = train length + platform length = 200 + platform. So platform = 500 - 200 = 300 m.

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