SOLUTION: An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip takes 4 hours against the wind. Find the speed of the plane in still air and the speed o

Question 722530: An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip takes 4 hours against the wind. Find the speed of the plane in still air and the speed of the wind.
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
An airplane takes 3 hours to travel a distance of 1680 miles with the wind. The return trip takes 4 hours against the wind. Find the speed of the plane in still air and the speed of the wind.
***
let x=speed of plane in still air
let c=speed of wind
x+c=speed of plane downwind
x-c=speed of plane upwind
travel time=distance/speed
..
1680/(x+c)=3
1680/(x-c)=4
..
3x+3c=1680
4x-4c=1680
..
12x+12c=4*1680=6720
12x-12c=3*1680=5040
add
24x=11760
x=490
3c=1680-3x
3c=1680-1470
3c=210
c=70
speed of plane in still air=490 mph
speed of wind=70 mph
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