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�s

Question 71560: 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 galactus(183) (Show Source): You can put this solution on YOUR website!
Use the d=rt formula.
t=d/r
You're given the time and distance.

Divide by 10:

Factor or use the quadratic formula. Let's factor:
What 2 numbers when added equal -144 and when multiplied equal -900
a+b=-144
ab=-900
150 and -6
(r-150)(r+6)=0
Since speed can't be negative, -6 is erroneous.
Therefore, the planes speed in still air is 150 mph

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