document.write( "Question 860331: A motorboat travels 147 in 3 hours going upstream. It travels 231 going downstream in the same amount of time. 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 #518339 by mananth(16946) $\"\"$ $\"About$

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motor boat speed =x mph
\n" ); document.write( "current speed =y mph
\n" ); document.write( "against current 3 hours
\n" ); document.write( "with current 3 hours
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\n" ); document.write( "Distance with current 231 miles distance against current 147
\n" ); document.write( "t=d/r against current (x-y)
\n" ); document.write( "147.00 / ( x - y )= 3.00
\n" ); document.write( "
\n" ); document.write( "3.00 x - -3.00 y = 147.00 ....................1
\n" ); document.write( "with current (x+y)
\n" ); document.write( "231.00 / ( x + y )= 3.00
\n" ); document.write( "3.00 ( x + y ) = 231.00
\n" ); document.write( "3.00 x + 3.00 y = 231.00 ...............2
\n" ); document.write( "Multiply (1) by 1.00
\n" ); document.write( "Multiply (2) by 1.00
\n" ); document.write( "we get 2.00
\n" ); document.write( "3.00 x + -3.00 y = 147.00
\n" ); document.write( "3.00 x + 3.00 y = 231.00
\n" ); document.write( "6.00 x = 378.00
\n" ); document.write( "/ 6.00
\n" ); document.write( "x = 63 mph
\n" ); document.write( "
\n" ); document.write( "plug value of x in (1) y
\n" ); document.write( "3 x -3 y = 147
\n" ); document.write( "189 -3 -189 = 147
\n" ); document.write( "-3 y = 147
\n" ); document.write( "-3 y = -42 mph
\n" ); document.write( " y = 14
\n" ); document.write( "motor boat 63 mph
\n" ); document.write( "current 14 mph
\n" ); document.write( " \n" ); document.write( "

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