<PRE><B>Question 175691</B>
a 6 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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Withwind DATA:
rate = 180+c ; distance = 7 mi ; time = d/r = 7/(180+c) hrs.
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againstwind DATA:
rate = 180-c ; distance = 5 mi ; time = d/r = 5/(180-c) hrs.
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EQUATION:
time = time = 7/(180+c) = 5/(180-c)
Cross-multiply
7(180-c) = 5(180+c)
7*180 - 7c = 5*180+5c
12c = 2*180
c = 2*15
c = 30 mph (speed of the wind)
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Cheers,
Stan H.</PRE>