document.write( "Question 872880: An airplane flew for 3 hours with a 20mph tail wind. The return flight against the same wind took 4 hours. Find the speed of the plane in still air.
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Algebra.Com's Answer #526496 by mananth(16946) $\"\"$ $\"About$

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plane speed x mph
\n" ); document.write( "wind speed 20 mph
\n" ); document.write( "..
\n" ); document.write( "against wind x- 20
\n" ); document.write( "with wind x+ 20
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\n" ); document.write( "against wind 4 hours
\n" ); document.write( "with wind 3 hours
\n" ); document.write( "Distance is same. D=r*t
\n" ); document.write( "4 ( x - 20 ) = 3 ( x + 20 )
\n" ); document.write( "4 x - 80 = 3 x + 60
\n" ); document.write( "4 x - 3 x = 80 + 60
\n" ); document.write( "1 x = 140
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\n" ); document.write( "x = 140 mph
\n" ); document.write( "plane speed = 140 mph
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