document.write( "Question 694675: An airplane flew for 4 hours with a 20-km/h tail wind. The return flight against the same wind took 5 hours. Find the speed of the plane still in air. \n" ); document.write( "
Algebra.Com's Answer #428134 by mananth(16946)\"\" \"About 
You can put this solution on YOUR website!
Plane speed x km/h
\n" ); document.write( "wind speed 20 km/h
\n" ); document.write( "..
\n" ); document.write( "against currentspeed x- 20
\n" ); document.write( "withcurrent x+ 20
\n" ); document.write( "..
\n" ); document.write( "Against current 5 hours
\n" ); document.write( "with current x+y 4 hours
\n" ); document.write( "Distance is same. D=r*t
\n" ); document.write( "5 ( x - 20 ) = 4 ( x + 20 )
\n" ); document.write( "5 x - 100 = 4 x + 80
\n" ); document.write( "5 x - 4 x = 100 + 80
\n" ); document.write( "1 x = 180
\n" ); document.write( "/ 1
\n" ); document.write( "x = 180 km/h
\n" ); document.write( "Plane speed = 180 km/h
\n" ); document.write( " \n" ); document.write( "
\n" );