Question

An aeroplane left 50 min later than its scheduled time, and in order to reach the destination ,1250km away ,in time ,it had to increase its speed by 250km/hr from its usual speed.Find its usual speed

Answer 1

Let 'x' be the usual speed of the aeroplane.
Increased speed of the plane = (x+250)
convert 50 mins to hours =50/60=5/6 hrs.
Time = distance / speed.
(1250/x) - 1250/(x+250)=5/6
[(1250(x+250) - 1250 x)/ (x(x+250)]=5/6

[(1250x +312500 -1250x) / (x² +250x)]=5/6
6(312500)=5(x² +250x)
1875000 =5x² +1250x
5x² +1250x -1875000=0
5(x-500)(x+750)=0
we get x= 500 and x= -750.
Since speed cannot be negative so discard the negative value
 we get x=500 km/hr.

so the usual speed of the  aeroplane  is 500 km/hr
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Answer 2

here is your answer.....