Multiple choice

A person is walking parallel to a railway line , at a speed of $5$ km/hr. A train travelling in opposite direction at $49$ km/hr, passes him in $12$ seconds. Find the length of the train.

  1. $160$ m
  2. $130$ m
  3. $120$ m
  4. $180$ m
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D Correct answer
Explanation

Relative speed = 49 + 5 = 54 km/hr = 54 * (5/18) = 15 m/s. Length of train = speed * time = 15 * 12 = 180 m.

AI explanation

Because the person and the train are moving in opposite directions, use the relative speed formula by adding their speeds, which gives 49 km/hr plus 5 km/hr equals 54 km/hr. Convert this relative speed to metres per second by multiplying by 5/18, yielding 15 m/s. The length of the train is the relative speed multiplied by the time it takes to pass the person. Calculate 15 m/s times 12 seconds to get a train length of 180 m.

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