document.write( "Question 771159: An airplane took 4 hours to fly 2400 miles against a head wind. the return trip with the wind took 3 hours. What is the speed of the plane in still air and the speed oof the wind? \n" ); document.write( "

Algebra.Com's Answer #469973 by mananth(16946) $\"\"$ $\"About$

You can put this solution on YOUR website!
Plane speed =x mph
\n" ); document.write( "wind speed =y mph
\n" ); document.write( "against wind 4 hours
\n" ); document.write( "with wind 3 hours
\n" ); document.write( "
\n" ); document.write( "Distance with wind 2400 miles distance against wind 2400
\n" ); document.write( "t=d/r against wind (x-y)
\n" ); document.write( "2400.00 / ( x - y )= 4.00
\n" ); document.write( "
\n" ); document.write( "4.00 x - -4.00 y = 2400.00 ....................1
\n" ); document.write( "with wind (x+y)
\n" ); document.write( "2400.00 / ( x + y )= 3.00
\n" ); document.write( "3.00 ( x + y ) = 2400.00
\n" ); document.write( "3.00 x + 3.00 y = 2400.00 ...............2
\n" ); document.write( "Multiply (1) by 3.00
\n" ); document.write( "Multiply (2) by 4.00
\n" ); document.write( "we get
\n" ); document.write( "12.00 x + -12.00 y = 7200.00
\n" ); document.write( "12.00 x + 12.00 y = 9600.00
\n" ); document.write( "24.00 x = 16800.00
\n" ); document.write( "/ 24.00
\n" ); document.write( "x = 700 mph
\n" ); document.write( "
\n" ); document.write( "plug value of x in (1) y
\n" ); document.write( "4 x -4 y = 2400
\n" ); document.write( "2800 -4 -2800 = 2400
\n" ); document.write( "-4 y = 2400
\n" ); document.write( "-4 y = -400 mph
\n" ); document.write( " y = 100
\n" ); document.write( "Plane 700 mph
\n" ); document.write( "wind 100 mph
\n" ); document.write( "
\n" ); document.write( "CHECK
\n" ); document.write( "x+y= 800
\n" ); document.write( "X-y= 600 +
\n" ); document.write( "2400.00 / ( 800.00 )= 3
\n" ); document.write( "2400 / ( 600 ) = 4
\n" ); document.write( " \n" ); document.write( "

\n" );