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Flying against the wind, an alrplane travels 4700 kilometers in 5 hours. Flying with the wind, the same plane travels 9520 kilometers in 7 hours. What is the rate of the plane in still air and what is the rate of the wind?​

 Sep 20, 2021
 #1
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4700 / (a-w) = 5         9520 / (a+w) = 7     <===== re-arrange to solve for 'a' :    (9520-7w) / 7 = a  = 1360 -w

Sub in the red equation for 'a' then solve for 'w' :

 

4700/ (1360-w - w) = 5

w = 210 km/hr

a = 1360 -210 = 1150 km/hr

 Sep 20, 2021
 #2
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4,700 / 5 ==940 km/h - its speed against the wind.

9,520 / 7==1,360 km/h - its speed with the wind.

 

[940  +  1,360] / 2 ==1,150 km/h - its speed in still air.

[1,360  -  940 ] / 2 ==210 km/h - speed of the wind.

 Sep 20, 2021

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