document.write( "Question 762811: a man can row 20 km downstream in the time it takes him to row 8 km upstream. he rows downstream for 1 and 1/2 hours, then turns and rows back for 3 hrs, but he finds that he will still 3 km from his starting place. find the rate of the man in still water and the rate of the stream. \n" ); document.write( "

Algebra.Com's Answer #464213 by lwsshak3(11628) $\"\"$ $\"About$

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a man can row 20 km downstream in the time it takes him to row 8 km upstream. he rows downstream for 1 and 1/2 hours, then turns and rows back for 3 hrs, but he finds that he will still 3 km from his starting place. find the rate of the man in still water and the rate of the stream.
\n" ); document.write( "***
\n" ); document.write( "let x=rate in still water
\n" ); document.write( "let c=rate of stream
\n" ); document.write( "(x+c)=rate downstream
\n" ); document.write( "(x-c)=rate upstream
\n" ); document.write( "travel time=distance/rate
\n" ); document.write( "distance=rate*travel time
\n" ); document.write( "..
\n" ); document.write( " $\"20%2F%28x%2Bc%29=8%2F%28x-c%29\"$
\n" ); document.write( "20x-20c=8x+8c
\n" ); document.write( "12x=28c
\n" ); document.write( "x=28c/12=7c/3
\n" ); document.write( "..
\n" ); document.write( "1.5(x+c)=3(x-c)+3
\n" ); document.write( "1.5x+1.5c=3x-3c+3
\n" ); document.write( "-1.5x+4.5c=3
\n" ); document.write( "plug in x=7c/3 from first equation
\n" ); document.write( "-1.5(7c/3)+4.5c=3
\n" ); document.write( "-7c/2+4.5c=3
\n" ); document.write( "-3.5c+4.5c=3
\n" ); document.write( "c=3
\n" ); document.write( "..
\n" ); document.write( "-1.5x+4.5*3=3
\n" ); document.write( "-1.5x+13.5=3
\n" ); document.write( "1.5x=10.5
\n" ); document.write( "x=7
\n" ); document.write( "rate in still water=7 km/hr
\n" ); document.write( "rate of stream=3 km/hr
\n" ); document.write( " \n" ); document.write( "

\n" );