A train passes two bridges of lengths $ 210 \mathrm{~m} $ and $ 122 \mathrm{~m} $ in 25 sec and 17 sec respectively. Calculate the length and speed of the train.


Given:

A train passes two bridge of lengths \( 210 \mathrm{~m} \) and \( 122 \mathrm{~m} \) in 25 sec and 17 sec respectively.

To do:

We have to find the length and speed of the train.

Solution:

Let the length of the train be $x$.

In both cases, the speed of the train is the same.

This implies,

It travels $(210+x)\ m$ in 25 sec and $(122+x)\ m$ in 17 sec.

We know that,

$Speed = \frac{Distance}{Time}$

Therefore,

$\frac{210 + x}{25} = \frac{122+x}{17}$

$17(210 + x) = 25(122 + x)$    (On cross multiplication)

$3570+17x=3050+25x$

$3570-3050 = 25x-17x$

$520=8x$

$x=\frac{520}{8}$

$x = 65\ m$

Therefore, the length of the train is 65 m.

$Speed = \frac{210+65}{25}$

$=\frac{275}{25}$

$= 11\ m/s$

The length of the train is 65 m and the speed of the train is 11 m/s.

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Updated on: 10-Oct-2022

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