SOLUTION: 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 hours, what is the plane's speed still in the

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Question 78171: 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 hours, what is the plane's speed still in the air?
Found 2 solutions by jim_thompson5910, scott8148:
Answer by jim_thompson5910(21685) About Me  (Show Source):
You can put this solution on YOUR website!
Take a look at this answer since it addresses the same question.

Answer by scott8148(5891) About Me  (Show Source):
You can put this solution on YOUR website!
let s=speed in still air ... (rate)*(time)=distance so t=d/r ... (time out)+(time back)=(total time)

(720/(s-30))+(720/(s+30))=10 ... multiplying by s%5E2-900 and dividing by 10 gives 72%28s%2B30%29%2B72%28s-30%29=s%5E2-900

distributing and rearranging terms gives s%5E2-144s-900=0 ... factoring gives (s-150)(s+6)=0 ... so s=150 mi/h