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 h, what is the plane’s speed in still air?
Algebra ->
Equations
-> 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 h, what is the plane’s speed in still air?
Log On
Question 119382:
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 checkley71(8403) (Show Source):
You can put this solution on YOUR website! 720/(r-30)+720/(r+30)=10
[720(r+30)+720(r-30)]/(r^2-900)=10
(720r+21,600+720r-21,600)/(r^2-900)=10 now cross multiply
10(r^2-9000)=1440r
10r^2-1440r-9000=0
10(r^2-144r-900)=0
10(x-150)(x+6)=0
x-150=0
x=150 for the speed of the airplane.
proof
720/(150-30)+720/(150+30)=10
720/120+720/180=10
6+4=10
10=10
(