A train takes 10 seconds to cross a man standing on a platform and 44 seconds to cross the platform.What is the length of the platform.What is the length of the platform if the speed of the train is 72 kmph?Correct answer is '440'. Can you explain this answer?

Question

Answer

Solution:

Let the length of the platform be 'x' and the length of the train be 'y'. Also, let the speed of the train be 'v'.

Case 1: When the speed of the train is not given.

Given, the train takes 10 seconds to cross a man standing on a platform.

=> Length of the train = Distance covered by the train in 10 seconds.

=> y = v × 10

Also, given, the train takes 44 seconds to cross the platform.

=> Length of the train and platform combined = Distance covered by the train in 44 seconds.

=> y + x = v × 44

Now, by solving these two equations we get:

=> x = (v × 44) - (v × 10)

=> x = v × 34

Therefore, the length of the platform is 34 times the speed of the train when the speed of the train is not given.

Case 2: When the speed of the train is given as 72 kmph.

We know that 72 kmph = 20 m/s (1 kmph = 5/18 m/s)

Now, substituting the value of 'v' as 20 in the above equation, we get:

=> x = 20 × 34

=> x = 680 meters

Therefore, the length of the platform is 680 meters when the speed of the train is 72 kmph.

Answer: 440 (given answer is incorrect)

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