document.write( "Question 580945: One plane at 520 feet is ascending at a rate of 40 feet per minute, while another plane at 3800 feet is descending at a rate of 120 feet per minute. How long will it take the two planes to be at the same altitude? \n" ); document.write( "
Algebra.Com's Answer #371407 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
One plane at 520 feet is ascending at a rate of 40 feet per minute, while another plane at 3800 feet is descending at a rate of 120 feet per minute.
\n" ); document.write( " How long will it take the two planes to be at the same altitude?
\n" ); document.write( ":
\n" ); document.write( "Let = time (in minutes) for this to be true
\n" ); document.write( ";
\n" ); document.write( "40t + 520 = 3800 - 120t
\n" ); document.write( "40t + 120t = 3800 - 520
\n" ); document.write( "160t = 3280
\n" ); document.write( "t = 3280/160
\n" ); document.write( "t = 20.5 minutes
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check this, find at what altitude they are equal
\n" ); document.write( "40(20.5) + 520 = 3800 - 120(20.5)
\n" ); document.write( "820 + 520 = 3800 - 2460
\n" ); document.write( "1340 = 1340 \n" ); document.write( "
\n" );