document.write( "Question 788146: the downriver trip is 36 km each way and takes 8 hours for thr trip. the upriver destination is 60 km away and take 10 hours to get there. find the speed of the boat in still water and the speed of the river \n" ); document.write( "
Algebra.Com's Answer #478415 by mananth(16946)\"\" \"About 
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The total trip takes 8 hours\r
\n" ); document.write( "\n" ); document.write( "rate downstream = b+c where b is boat speed and c is current speed\r
\n" ); document.write( "\n" ); document.write( "rate upstream = b-c\r
\n" ); document.write( "\n" ); document.write( "downstream
\n" ); document.write( "36/(b+c)+36/(b-c)=8\r
\n" ); document.write( "\n" ); document.write( "substitute 1/(b+c) =x
\n" ); document.write( "1/(b-c)=y
\n" ); document.write( "36x+36y=8\r
\n" ); document.write( "\n" ); document.write( "Upstream is 60 km\r
\n" ); document.write( "\n" ); document.write( "60/(b-c)=10\r
\n" ); document.write( "\n" ); document.write( "let 1/(b-c)=y\r
\n" ); document.write( "\n" ); document.write( "60y=10
\n" ); document.write( "y=1/6\r
\n" ); document.write( "\n" ); document.write( "substitute y in 36x+36y=8
\n" ); document.write( "36x+36/6 =8
\n" ); document.write( "36x=2
\n" ); document.write( "x=1/18
\n" ); document.write( "1/(b-c)=1/18
\n" ); document.write( ".
\n" ); document.write( "b+c=18
\n" ); document.write( "b-c=6
\n" ); document.write( "add the equations\r
\n" ); document.write( "\n" ); document.write( "2b=24
\n" ); document.write( "b=12km/h speed of boat
\n" ); document.write( "plug b to get c speed of current\r
\n" ); document.write( "\n" ); document.write( "m.ananth@hotmail.ca\r
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\n" ); document.write( "\n" ); document.write( "2b=
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