SOLUTION: An airplane flies 490 miles with the wind and 330 against the wind in the same length of time. If the speed of the wind is 20, what is the speed of the airplane in still air?

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Question 344122: An airplane flies 490 miles with the wind and 330 against the wind in the same length of time. If the speed of the wind is 20, what is the speed of the airplane in still air?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
D=RT
490=(R+20)T
T=490/(R+20)
330=(R-20)T
T=330/(R-20)
490/(R+20)=330/(R-20) CROSS MULTIPLY.
490(R-20)=330(R+20)
490R-9,800=330T+6,600
490R-330R=6,600+9,800
160R=16,400
R=16,400/160
R=102.5 MPH IS THE PLANES SPEED IN STILL AIR.
PROOF:
490/(102.5+20)=330/(102.5-20)
490/122.5=330/82.5
4=4