document.write( "Question 568269: A boat traveled 108 miles downstream and back. The trip downstream took 4 hours. The trip back took 12 hours. Find the speed of the boat in still water and the speed of the current. \n" ); document.write( "

Algebra.Com's Answer #366888 by mananth(16946) $\"\"$ $\"About$

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Boat speed =x mph
\n" ); document.write( "current speed =y mph
\n" ); document.write( "against current x-y 12.00 hours
\n" ); document.write( "with current x+y 4.00 hours
\n" ); document.write( "
\n" ); document.write( "Distance = same= 108 miles
\n" ); document.write( "t=d/r
\n" ); document.write( "108 / ( x - y )= 12.00
\n" ); document.write( "12 ( x - y ) = 108.00
\n" ); document.write( "12 x -12 y = 108 ....................1
\n" ); document.write( "108 / ( x + y )= 4.00
\n" ); document.write( "4.00 ( x + y ) = 108
\n" ); document.write( "4.00 x + 4.00 y = 108 ...............2
\n" ); document.write( "Multiply (1) by 1
\n" ); document.write( "Multiply (2) by 3
\n" ); document.write( "we get
\n" ); document.write( "12 x -12 y = 108
\n" ); document.write( "12 x + 12 y = 324
\n" ); document.write( "24 x = 432
\n" ); document.write( "/ 24
\n" ); document.write( "x = 18 mph
\n" ); document.write( "
\n" ); document.write( "plug value of x in (1)
\n" ); document.write( "12 x -12 y = 108
\n" ); document.write( "216 -12 y = 108
\n" ); document.write( "-12 y = 108 -216
\n" ); document.write( "-12 y = -108
\n" ); document.write( " y = 9
\n" ); document.write( "The speed of Boat = 18 mph
\n" ); document.write( "The speed of current = 9 mph
\n" ); document.write( "m.ananth@hotmail.ca
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