document.write( "Question 924344: A motorboat takes as long to go 12 miles downstream as to go 8 miles upstream. The river has a current of 3 miles per hour. What is the rate of the boat in still water? \n" ); document.write( "

Algebra.Com's Answer #560767 by TimothyLamb(4379) $\"\"$ $\"About$

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x = boat speed in still water
\n" ); document.write( "y = current speed = 3 mph
\n" ); document.write( "---
\n" ); document.write( "down:
\n" ); document.write( "x + y = 12/t
\n" ); document.write( "---
\n" ); document.write( "up:
\n" ); document.write( "x - y = 8/t
\n" ); document.write( "---
\n" ); document.write( "x + y = 12/t
\n" ); document.write( "x - y = 8/t
\n" ); document.write( "---
\n" ); document.write( "x = 12/t - y
\n" ); document.write( "x = 8/t + y
\n" ); document.write( "---
\n" ); document.write( "x = 12/t - 3
\n" ); document.write( "x = 8/t + 3
\n" ); document.write( "---
\n" ); document.write( "12/t - 3 = 8/t + 3
\n" ); document.write( "12/t - 8/t = 6
\n" ); document.write( "4/t = 6
\n" ); document.write( "t = 4/6
\n" ); document.write( "---
\n" ); document.write( "x = 12/t - 3
\n" ); document.write( "x = 12/(4/6) - 3
\n" ); document.write( "x = 18 - 3
\n" ); document.write( "---
\n" ); document.write( "answer:
\n" ); document.write( "x = 15 mph
\n" ); document.write( "---
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