document.write( "Question 825285: an airplane makes a 990 km flight with a tailwind and returns, flying into the same wind. The total flying time is 3 hours 20 minutes, and the airplane's speed in still air is 600 km/h. What is the speed of the wind? \n" ); document.write( "
Algebra.Com's Answer #497196 by stanbon(75887)\"\" \"About 
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an airplane makes a 990 km flight with a tailwind and returns, flying into the same wind. The total flying time is 3 hours 20 minutes, and the airplane's speed in still air is 600 km/h. What is the speed of the wind?
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\n" ); document.write( "up-wind DATA: rate = 600-w km/hr ; distance = 990 km ; time = 990/(600-w) hrs.
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\n" ); document.write( "down-wind DATA: rate = 600+w km/hr ; distance = 990 km ; time = 990/(600+w) hrs.
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\n" ); document.write( "Equation::
\n" ); document.write( "time + time = 3 1/3 = 10/3 hrs
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\n" ); document.write( "990/(600-w) + 990/(600+w) = 10/3
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\n" ); document.write( "3*990(600-w) + 3*990(600+w) = 10(600^2-w^2)
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\n" ); document.write( "3*99(600-w) + 3*99(600+w) = 600^2-w^2
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\n" ); document.write( "2*3*99*600 = 600^2-w^2
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\n" ); document.write( "w^2 = 3600
\n" ); document.write( "w = 60 km/hr (wind speed)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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