Question 352017: a pilot can fly an airplane 1080 miles with the wind in the same time as she can fly 1000 miles against the wind. if the speed of the wind is 20 mph, find the speed of the plain still in still air.
Answer by checkley77(12844)   (Show Source):
You can put this solution on YOUR website! D=RT
1080=(R+20)T
T=1080/(R+20) FOR THE TRUIP WITH THE WIND.
1000=(R-20)T
T=1000/(R-20) FOR THE TRIP QGAINST THE WIND.
1080/(R+20)=1000/(R-20) CROSS MULTIPLY
1080(R-20)=1000(R+20)
1,080R-21,600=1,000R+20,000
1,080R-1,000R=20,000+21,600
80R=41,600
R=41,600/80
R=520 MPH. IS THE SPEED OF THE PLANE IN STILL AIR.
PROOF:
1,080/(520+20)=1,000/(520-20)
1,080/540=1,000/500
2=2
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