document.write( "Question 549707: A boat traveled 72 miles downstream and back. The trip downstream took 3 hours. The trip back took 12 hours. Find the speed of a boat in still water and the speed of a current. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #357966 by mananth(16946)\"\" \"About 
You can put this solution on YOUR website!
Boat speed =x mph
\n" ); document.write( "current speed =y mph
\n" ); document.write( "against current , x-y 12 hours
\n" ); document.write( "with current , x+y 3 hours
\n" ); document.write( "
\n" ); document.write( "Distance = same= 72 miles
\n" ); document.write( "t=d/r against current
\n" ); document.write( "72 / ( x - y )= 12.00
\n" ); document.write( "12 ( x - y ) = 3.00
\n" ); document.write( " With current
\n" ); document.write( "12 x -12 y = 72 ....................1
\n" ); document.write( "72 / ( x + y )= 3.00
\n" ); document.write( "3.00 ( x + y ) = 72
\n" ); document.write( "3.00 x + 3 y = 72 ...............2
\n" ); document.write( "Multiply (1) by 1.00
\n" ); document.write( "Multiply (2) by 4.00
\n" ); document.write( "we get
\n" ); document.write( "12 x + -12 y = 72
\n" ); document.write( "12 x + 12 y = 288
\n" ); document.write( "24 x = 360
\n" ); document.write( "/ 24
\n" ); document.write( "x = 15 mph
\n" ); document.write( "
\n" ); document.write( "plug value of x in (1)
\n" ); document.write( "12 x -12 y = 72
\n" ); document.write( "180 -12 y = 72
\n" ); document.write( "-12 y = 72 -180
\n" ); document.write( "-12 y = -108
\n" ); document.write( " y = 9 mph
\n" ); document.write( " Boat 15 mph
\n" ); document.write( " current 9 mph
\n" ); document.write( "
\n" ); document.write( "m.ananth@hotmail.ca
\n" ); document.write( " \n" ); document.write( "
\n" );