Question

an aeroplane covers a distance of 720 km with a uniform speed. if its speed is increased by 10 km per hour it would have taken 1 hour less to cover the same distance. find the speed of the aeroplane​

Answer 1

Answer:

Total Distance = 720km

According to the condition :-

720/x -720/x+10 =1

1/x - 1/x+10 = 1/720

Taking LCM in LHS

x+10-x/x^2+10x = 1/720

10/ x^2+10x = 1/720

by Cross Multiplication

10(720) = x^2+10x

7200 = x^2+10x

x^2+10x - 7200 = 0

x^2+90x-80x -7200 = 0

x(x+90) - 80(x+90) = 0

(x-80) (x+90) = 0

x = 80

x = -90

Reject -90

x = 80

therefore, the speed of aeroplane is 80km/h