Question 173418
A six-passenger plane cruises at 180 mph in
calm air. If the plane flies 7 miles with the wind in the
same amount of time as it flies 5 miles against the wind,
then what is the wind speed? 
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Yes, use d= rt
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With-wind DATA:
distance = 7 miles; rate = 180+wind ; time = d/r = 7/(180+w) hrs
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Against-wind DATA:
distance = 5 miles ; rate = 180-w ; time = d/r = 5/(180-w) hrs
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time = time
7/(180+w) = 5/(180-w)

7(180-w) = 5(180+w)
7*180 - 7w= 5*180 + 5w
12w = 2*180
w = 2*15
wind speed = 30 mph
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Cheers,
Stan H.