SOLUTION: Science and medicine. A plane flies 720 mi against a steady 30-mi/h headwind and then returns to the same point with the wind. If the entire trip takes 10 h, what is the plane&#82

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Question 111836: Science and medicine. A plane flies 720 mi against a steady 30-mi/h headwind
and then returns to the same point with the wind. If the entire trip takes 10 h, what is the plane’s speed in still air?
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
let x=speed ___ time=distance/rate ___ total time is 10

(720/(x-30))+(720/(x+30))=10 ___ (720(x+30))+(720(x-30))=10(x^2-30^2)

x^2-144x-900=0 ___ (x-150)(x+6)=0