Multiple choice

Ankit is standing on a 180 m long railway platform and he observes that a train crosses the platform in 20 seconds and him in 8 seconds. The speed of the train is

  1. 54 km/hr

  2. 50 km/hr

  3. 52 km/hr

  4. 62 km/hr

  5. 60 km/hr
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let L be train length and v be speed. L/v = 8 and (L+180)/v = 20. L = 8v. (8v+180)/v = 20. 8v+180 = 20v. 12v = 180. v = 15 m/s. Convert to km/hr: 15 * 18/5 = 54 km/hr.

AI explanation

Let the length of the train be L meters. Using the formula speed equals distance divided by time, the speed of the train is L divided by 8 when crossing Ankit, and (L plus 180) divided by 20 when crossing the platform. Setting these equal gives L divided by 8 equals (L plus 180) divided by 20, which simplifies to 20L equals 8L plus 1440, meaning 12L equals 1440, so the length L is 120 m. The speed of the train is 120 divided by 8, giving 15 m/s, and multiplying by 18 over 5 converts this to 54 km/hr.

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