SOLUTION: A plane flies 500 miles with the wind and 340 miles against the wind in the same length of time. If the speed of the wind is 20 mph, what is the speed of the plane in still air?

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Question 667387: A plane flies 500 miles with the wind and 340 miles against the wind in the same length of time. If the speed of the wind is 20 mph, what is the speed of the plane in still air?
Found 2 solutions by ewatrrr, stanbon:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

 t =D/r, time the same

+500%2F%28v%2B20%29+=+340%2F%28v-20%29  ||| Cross Multiply to solve for v

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A plane flies 500 miles with the wind and 340 miles against the wind in the same length of time. If the speed of the wind is 20 mph, what is the speed of the plane in still air?
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With wind DATA:
dist = 500 miles; rate = p+20 mph ; time = 500/(p+20) hrs
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Against wind DATA:
dist = 340 miles ; time = p-20 mph ; time = 340/(p-20) hrs
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Equation:
time = time
500/(p+20) = 340/(p-20)
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500p - 10000 = 340p + 6800
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160p = 16800
p = 105 mph (speed of the plane in still air)
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Cheers,
Stan H.
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