Q25 of 52 Page 1

In a flight of 2800 km, an aircraft was slowed down due to bad weather. Its average speed is reduced by 100 km/h and time increased by 30 minutes. Find the original duration of the flight.

Given,


Distance = 2800 km


Time increased by = 30 min. or 30/60 hr


Let the average speed of the aircraft = x km/hr


The reduced speed of the aircraft = (x – 100) km/hr


As we know;


Time = Distance/Speed


According to the question,




x2 – 100x = 560000


x2 – 100x – 560000 = 0


x2 – 800x + 700x – 560000 = 0


x (x – 800) + 700 (x – 800) = 0


(x – 800) (x + 700) = 0


x – 800 = 0 or x + 700 = 0


x = 800 or x = - 700


As speed of the aircraft cannot be negative,


Speed = 800 km/hr


Therefore,


Original duration = Distance/Speed


= 2800/800 = 7/2 hrs


Or 3 hrs and 30 mins.


Or 210 mins.


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