Question 698858
They often fly from Philly to Chicago, a distance of 780 miles.
On one particular trip they fly into the wind and the flight takes 2 hours
The return trip, with the wind is behind them, only takes 2 hours. 
If the wind speed is the same on each trip,
Find the speed of the wind and
Find the speed of the plane in still air.
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Same time --> no wind
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Find the speed of the plane in still air.
THAT'S CALLED AIRSPEED, NOT the speed of the plane in still air.
= 780/2 = 390 mi/hr