A train passes a platform in 36 seconds and a pedestrian in 20 seconds at 54 km/hr. What is the length of
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Answer: C. 240
Explanation
A train traveling at fifty four kilometers per hour converts to a speed of fifteen meters per second. Passing a pedestrian in twenty seconds means the train length equals fifteen meters per second multiplied by twenty seconds. Passing a platform in thirty six seconds gives a total distance of five hundred forty meters, leaving two hundred forty meters for the platform. Unit conversion from kilometers per hour to meters per second requires multiplying by five over eighteen. When a train passes a point pedestrian, the distance covered equals the total length of the train itself. When a train passes a platform, the total distance covered equals the sum of the train length and platform length.
One hundred twenty meters represents only half of the actual platform length calculated from the time difference. Two hundred sixty meters contains an arithmetic error in the subtraction of the train length from total distance. Two hundred twenty meters underestimates the platform length due to a minor miscalculation in the speed conversion step.
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