Question 1091730
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<pre>
Let x be the train' speed, in km/h


Then the plane speed is 2x km per hour.


The train spends {{{240/x}}} hours to cover the distance of 240 km.


The plane spends {{{240/(2x)}}} hours for the same trip.


The condition says that the difference in time is 1 hour:

{{{240/x}}} - {{{240/(2x)}}} = 1.


Multiply bot sides by 2x. You will get

2*240 - 240 = 2x  ====>  2x = 240   ====>  x = {{{240/2}}} = 120.


Thus you found the speed of the train. It is 120 km/h.


Then the speed of the plane is 2*120 = 240 km/h.
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Solved.


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