Question 613233: A plane can travel 640 miles against the wind in the same time it can travel 800 miles with the wind. If the plane can fly 180 mph in calm air, what is the speed of the wind?
If x represents the speed of the wind, which expression represents the time it takes for the plane to travel the 640 miles against the wind?
Answer by nerdybill(7384)   (Show Source):
You can put this solution on YOUR website! A plane can travel 640 miles against the wind in the same time it can travel 800 miles with the wind. If the plane can fly 180 mph in calm air, what is the speed of the wind? If x represents the speed of the wind, which expression represents the time it takes for the plane to travel the 640 miles against the wind?
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applying the "distance formula" of d=rt
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(180-x)t = 640 (equation 1)
(180+x)t = 800 (equation 2)
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solve equation 1 for t:
(180-x)t = 640
t = 640/(180-x)
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subsitute above into equation 2 and solve for x:
(180+x)t = 800
(180+x)(640/(180-x)) = 800
(180+x)640 = 800(180-x)
115200+640x = 144000-800x
115200+1440x = 144000
1440x = 144000-115200
1440x = 28800
x = 28800/1440
x = 20 mph (speed of wind)
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