document.write( "Question 910265: a boat takes 4 hours to go 640km downstream. it takes the same to go 240 km upstream. find the speed of boat in still water and the speed of the stream. \n" ); document.write( "
Algebra.Com's Answer #552347 by richwmiller(17219)\"\" \"About 
You can put this solution on YOUR website!
r*t=d
\n" ); document.write( "with the current
\n" ); document.write( "(r+c)*4=640
\n" ); document.write( "(r+c)=640/4
\n" ); document.write( "r+c=160
\n" ); document.write( "against the current
\n" ); document.write( "(r-c)*4=240
\n" ); document.write( "(r-c)=240/4\r
\n" ); document.write( "\n" ); document.write( "r-c=60
\n" ); document.write( "r+c=160
\n" ); document.write( "add
\n" ); document.write( "r+r=60+160
\n" ); document.write( "2r=220
\n" ); document.write( "r=110
\n" ); document.write( "r=110 boat\r
\n" ); document.write( "\n" ); document.write( "110-c=60
\n" ); document.write( "c=110-60
\n" ); document.write( "c=50 current
\n" ); document.write( "check
\n" ); document.write( "(110+50)*4=640
\n" ); document.write( "160*4=640
\n" ); document.write( "640=640
\n" ); document.write( "ok
\n" ); document.write( "(r-c)*4=240
\n" ); document.write( "(110-50)*4=240
\n" ); document.write( "60*4=240
\n" ); document.write( "240=240
\n" ); document.write( "ok\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "
\n" );