Find the length of a train if it takes 10 seconds to cross a pole and double of

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Question
Find the length of a train if it takes 10 seconds to cross a pole and double of this time to cross a platform of length 200 mts ?
Options
A. 180 mts
B. 190 mts
C. 200 mts
D. 210 mts

Correct Answer

200 mts

Explanation

Let the length of the train be 'L' mts

let the speed of the train be 'S' m/s

Given it crosses a pole in 10 sec=> L/S = 10 ......(1)
Given it takes 20 sec (double of pole) to cross a platform of length 200 mts

=> (L + 200)/S = 20

=> L/S + 200/S = 20

But from (1) L/S = 10

=> 200/S = 20 - 10

=> S = 20 m/s

Then, from (1)

=> L = 10 x 20 = 200 mts.

Hence, the length of the train = 200 mts.

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AIEEE