SOLUTION: A plane flies 720 mi against a steady 30-mi/h head-wind and then returns to the same point with the wind. If the entire trip takes 10 hr, what is the plane's speed in still air?
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Question 964017: A plane flies 720 mi against a steady 30-mi/h head-wind and then returns to the same point with the wind. If the entire trip takes 10 hr, what is the plane's speed in still air? Answer by lwsshak3(11628) (Show Source):
You can put this solution on YOUR website! A plane flies 720 mi against a steady 30-mi/h head-wind and then returns to the same point with the wind. If the entire trip takes 10 hr, what is the plane's speed in still air?
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let x=plane's speed in still air
(x+30)=plane's speed with the wind
(x-30)=plane's speed against the wind
travel time=distance/speed
lcd:(x+30)(x+30)=(x^2-900)
720x+21600+720x-21600=10(x^2-900)
1440x=10x^2-9000
10x^2-1440x-9000=0
x^2-144x-900=0
(x-150)(x+6)=0
x=150
what is the plane's speed in still air? 150 mph
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