document.write( "Question 767511: A motorboat travels 756 mi in 9 hours going upstream and 684 mi in 6 hours going downstream. What is the rate of the boat in still water and what is the rate of the current? \n" ); document.write( "
Algebra.Com's Answer #467649 by lwsshak3(11628)\"\" \"About 
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A motorboat travels 756 mi in 9 hours going upstream and 684 mi in 6 hours going downstream. What is the rate of the boat in still water and what is the rate of the current?
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\n" ); document.write( "let x=rate of speed of motorboat in still water
\n" ); document.write( "let c=rate of speed of current
\n" ); document.write( "x+c=rate of speed of motorboat downstream
\n" ); document.write( "x-c=rate of speed of motorboat upstream
\n" ); document.write( "travel time=distance/rate of speed
\n" ); document.write( "...
\n" ); document.write( "756/(x-c)=9
\n" ); document.write( "684/(x+c)=6
\n" ); document.write( "..
\n" ); document.write( "9x-9c=756
\n" ); document.write( "6x+6c=684
\n" ); document.write( "..
\n" ); document.write( "54x-54c=4536
\n" ); document.write( "54x+54c=6156
\n" ); document.write( "add
\n" ); document.write( "108x=10692
\n" ); document.write( "x=99
\n" ); document.write( "6c=684-6x=684-594=90
\n" ); document.write( "c=15
\n" ); document.write( "rate of speed of motorboat in still water=99 mph
\n" ); document.write( "rate of speed of current=15 mph
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