SOLUTION: I don't usually have trouble with these, but even with my little chart, I'm getting confused on how set up the problem. A plane flies 720 mi against a steady 30 mi/h headwind

Question 46935This question is from textbook Beginning Algebra
: I don't usually have trouble with these, but even with my little chart, I'm getting confused on how set up the problem.

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 10h, what is the plane's speed in still air? This question is from textbook Beginning Algebra

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
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 10h, what is the plane's speed in still air?
WITH THE WIND DATA:
distance =720 mi ; rate= plane speed +30 ; time =d/r= 720/(p+30)
AGAINST THE WIND DATA:
distance = 720 mi ; rate = plane speed -30; time = d/r = 720/(p-30)
EQUATION:
720/(p+30) + 720/(p-30) = 10
72/(p+30) + 72/(p-30) = 1
72p-72*30+72p+72*30 = (p+30)(p-30)
144p=p^2-900
p^2-144p-900=0
(p-150)(P+6)=0
p=150 mph. ( The plane's speed in still air is 150 mph)
Cheers,
Stan H.
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