SOLUTION: A spy plane flies over 600km and back all in six hours and 20 minutes. if on the trip, a wind of 10kph was with it and against its return course, what was the speed of the spy pla

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Question 889540: A spy plane flies over 600km and back all in six hours and 20 minutes.
if on the trip, a wind of 10kph was with it and against its return course, what was the speed of the spy plane in still air?
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
A spy plane flies over 600km and back all in six hours and 20 minutes.
if on the trip, a wind of 10kph was with it and against its return course, what was the speed of the spy plane in still air?
***
let x=speed of plane in still air
x+10=speed of plane with wind
x-10=speed of plane against wind
travel time=distance/speed
6 hrs and 20 min=6 1/3 hrs=19/3 hrs
..
600%2F%28x%2B10%29%2B600%2F%28x-10%29=19%2F3
lcd=(x+10)(x-10)
(600)(x-10)+600(x+10)=19(x^2-100)/3
600x-6000+600x+6000=(19x^2-1900)/3
1200x=(19x^2-1900)/3
3600x=19x^2-1900
19x^2-3600x-1900=0
(x-190)(19x+10)=0 (got this from a graphics program)
19x+10=0
x=-10/19(reject)
or
x=190
speed of plane in still air=190 km/hr