Multiple choice

A train passes a 100 meters long platform in 28 seconds and a man standing on the platform in 20 seconds. The speed of the train is: একটি ট্রেন একটি 100 মিটার লম্বা প্লাটফর্ম কে 28 সেকেন্ডে এবং প্লাটফর্মে দাঁড়িয়ে থাকা এক ব্যক্তি কে 20 সেকেন্ডে অতিক্রম করে তাহলে ট্রেনটিি দৈর্ঘ্য

  1. 45 km./hr

  2. 50 km./hr

  3. 60 km./hr

  4. 40 km./hr
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A Correct answer
Explanation

Let the train length be L metres and its speed be v metres per second. Passing a man gives L = 20v, while passing the platform gives L + 100 = 28v. Solving gives v = 12.5 m/s, which equals 45 km/h.

AI explanation

Let the length of the train be L and its speed be S; using the formula distance equals speed multiplied by time, the train passing a man gives L equals 20S. When passing the 100-meter platform, the total distance is L plus 100, so L plus 100 equals 28S. Substituting the first equation into the second yields 20S plus 100 equals 28S, meaning the speed S is 12.5 m/s. Converting this to kilometers per hour gives 12.5 multiplied by 18/5, resulting in a speed of 45 km/hr.

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