help me solve this question.It is a word problem of class 8 algebra.Please provide the solution.
A plane flies between two points that are 700 km apart travelling with a wind speed of 25  km an hour when going with it and against it when returning.The onward trip takes 15 minutes less time than the return flight.What is the speed of the plane in still air ?

Dear student,

Please find below the solution to the asked query:

Let the speed of the plane in stil air be x km/hrThe speed of the air is given to be  25 km/hrThen the total speed of the plane while going is x+25 km/hrand the total speed of the plane while returning is x-25 km/hrThis implies that the time taken to cover a distance of 700 km while going is 700x+25and Time taken to cover a distance of 700 km while going is 700x-25According to given condition,   700x-25-700x+25=1560  15min=1560 hrsSimplify further to get,   7001x-25-1x+25=1560  700x+25-x+25x-25x+25=1560       700×50  x2-625=1560         35000x2-625=14Cross multiply to get,  x2-625=35000×4  x2-625=140000  x2=140625  x=140625  x=375This implies that the speed of the plane in stil air is 375 km/hr

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