A man standing on a railway platform noticed that a train took 21 seconds to cross the platform (this means the time elapsed from the moment the engine enters the platform till the last compartment leaves the platform) which is 88 meters long and that it took 9 seconds to pass him. Assuming that the train was moving with uniform speed. What is the length of the train in meters?

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answer is C.

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Detailed Solution

Concept- Assume that the train has a length of

meters and travels at a speed of

. There are two cases here. In the first scenario, it is assumed that the train needs 21 seconds to traverse the 88-meter-long platform. The train travels a distance equal to the sum of its own length and the platform's length in order to traverse it. To get an equation in terms of

and

, apply the formula Time

.In the second case, it is given that the train takes 9 seconds to cross a man standing on the platform. The train covers the distance equal to the length of the train to cross a man standing on the platform. Now, use the formula, Time

and get an equation in terms of

and

. Now, we have two equations in terms of

and

, and then, solve it further to get the value of