Question 1209198
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It took a train 65 seconds from starting to cross an iron bridge of length 1440 m 
to completely pass over the bridge. 
It also took the train 75 seconds from when it entered a 1680m tunnel to completely 
pass through the tunnel. 
Find the length and speed of the train. 
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<pre>
Let L be the length of the train (in meters),
and let V be the speed of the train, in meters per second.


For passing the bridge, we have this equation

    L + 1440 = 65*V.    (1)


For passing the tunnel, we have this equation

    L + 1680 = 75*V.    (2)


Subtract equation (1) from equation (2).  You will get

    1680 - 1440 = 75V - 65V,

        240     =     10V

          V     =     240/10 = 24.


The train speed is 24 m/s,  or  {{{24*(3600/1000)}}} = 86.4 kilometers per hour.


The length of the train, from equation (1), is

    L = 65*24 - 1440 = 120 meters.
</pre>

Solved.


I appreciate the fact that the input numbers are reasonable.


My great congratulations to the problem's composer.