document.write( "Question 483812: an airplane flew 660 miles with the wind, and then took 40 minutes longer for the return flight against the wind. if the plane flies 200 miles per hour in still air, find the speed of the wind. \n" ); document.write( "

Algebra.Com's Answer #331083 by mananth(16946) $\"\"$ $\"About$

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x= wind speed
\n" ); document.write( "against wind speed = 200-x
\n" ); document.write( "with wind speed = 200+x
\n" ); document.write( "t=d/r
\n" ); document.write( "time return - time forward = 2/3\r
\n" ); document.write( "\n" ); document.write( "660/(200-x)-660/(200+x)=2/3\r
\n" ); document.write( "\n" ); document.write( "LCD = 3(200-x)(200+x)\r
\n" ); document.write( "\n" ); document.write( "Multiply by the LCD\r
\n" ); document.write( "\n" ); document.write( "3*660(200+x)-3*660(200-x)=2/3 * (200-x)(200+x)\r
\n" ); document.write( "\n" ); document.write( "1980*200+ 1980x-1980*200+1980x=2(200-x)(200+x)\r
\n" ); document.write( "\n" ); document.write( "3960x=80000-2x^2\r
\n" ); document.write( "\n" ); document.write( "2x^2+3960x-80000=0
\n" ); document.write( "/2
\n" ); document.write( "x^2+1980x-40000=0\r
\n" ); document.write( "\n" ); document.write( "Find the roots of the equation by quadratic formula
\n" ); document.write( "
\n" ); document.write( "a= 1 b= 1980 c= -40000
\n" ); document.write( "
\n" ); document.write( "b^2-4ac= 3920400 - 160000
\n" ); document.write( "b^2-4ac= 4080400
\n" ); document.write( " $\"sqrt%28%094080400%09%29\"$ = 2020
\n" ); document.write( " $\"x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"$
\n" ); document.write( " $\"x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29\"$
\n" ); document.write( "x1=( -1980 + 2020 )/ 2
\n" ); document.write( "x1= 20
\n" ); document.write( "x2=( -1980 -2020 ) / 2
\n" ); document.write( "x2= -2000
\n" ); document.write( "Ignore negative value
\n" ); document.write( "x = 20 mph wind speed
\n" ); document.write( "m.ananth@hotmail.com
\n" ); document.write( " \n" ); document.write( "

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