document.write( "Question 68899: It takes a boat 4 hours to travel 56 miles down a river, and 3 hours longer to make the return trip. Find the speed of the current. \n" ); document.write( "

Algebra.Com's Answer #49041 by rmromero(383) $\"\"$ $\"About$

You can put this solution on YOUR website!
It takes a boat 4 hours to travel 56 miles down a river, and 3 hours longer to make the return trip. Find the speed of the current.
\n" ); document.write( "


\n" );
document.write( "What is asked in the problem?
\n" );
document.write( "Find the speed of the current?\r
\n" );
document.write( "\n" );
document.write( "Given:
\n" );
document.write( "It takes a boat 4 hours to travel 56 miles down the river
\n" );
document.write( "3 hours longer to make a return trip.\r
\n" );
document.write( "\n" );
document.write( "Representation:
\n" );
document.write( "Let x = speed of the boat in still water 
\n" );
document.write( "    y = speed of the current\r
\n" );
document.write( "\n" );
document.write( "Make a table for the information given:
\n" );
document.write( "                 r         t      =      d
\n" );
document.write( "Downstream      x+y        4      =      56
\n" );
document.write( "Upstream        x-y       4+3     =      56\r
\n" );
document.write( "\n" );
document.write( "Write an Equation:
\n" );
document.write( "4 (x + y) = 56
\n" );
document.write( "7 (x - y) = 56\r
\n" );
document.write( "\n" );
document.write( "       x + y = 14
\n" );
document.write( "       x - y = 8
\n" );
document.write( "       __________\r
\n" );
document.write( "\n" );
document.write( "          2x = 22
\n" );
document.write( "           x = 11 miles/hour   <<<<< speed of the boat in still water\r
\n" );
document.write( "\n" );
document.write( " x + y = 14
\n" );
document.write( "11 + y = 14
\n" );
document.write( "     y = 3 miles/hour <<<<<<<<< speed of the current\r
\n" );
document.write( "\n" );
document.write( "Checking:    
\n" );
document.write( "4 (x + y) = 56 , x = 11, y = 3
\n" );
document.write( "4(11 + 3) = 56
\n" );
document.write( "    4(14) = 56
\n" );
document.write( "       56 = 56 ----------->> True\r
\n" );
document.write( "
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( "7 (x - y) = 56, x = 11, y = 3
\n" );
document.write( "7(11 - 3) = 56
\n" );
document.write( "    7 (8) = 56
\n" );
document.write( "       56 = 56  ------->> True\r
\n" );
document.write( "\n" );
document.write( " \n" );
document.write( "

\n" );