document.write( "Question 199864: if a boat goes downstream 72 miles in 3 hours and upstream 60 miles in 6 hours, the rate of the river and the rate of the boat in still wtaer respectively are ? \n" ); document.write( "
Algebra.Com's Answer #150257 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
if a boat goes downstream 72 miles in 3 hours and upstream 60 miles in 6 hours,
\n" ); document.write( " the rate of the river and the rate of the boat in still water respectively are ?
\n" ); document.write( ":
\n" ); document.write( "Let x = boat speed in still water
\n" ); document.write( "Let y = rate of the current
\n" ); document.write( "then
\n" ); document.write( "(x+y) = speed down stream
\n" ); document.write( "(x-y) = speed up stream
\n" ); document.write( ":
\n" ); document.write( "Write a distance equation for each trip: time * speed = dist
\n" ); document.write( ":
\n" ); document.write( "3(x+y) = 72
\n" ); document.write( "6(x-y) = 60
\n" ); document.write( ":
\n" ); document.write( "Simplify both equations;
\n" ); document.write( "divide the 1st equation by 3,
\n" ); document.write( "divide the 2nd equation by 6
\n" ); document.write( "results:
\n" ); document.write( "x + y = 24
\n" ); document.write( "x - y = 10
\n" ); document.write( "---------------addition eliminates y, find x
\n" ); document.write( "2x = 34
\n" ); document.write( "x = \"34%2F2\"
\n" ); document.write( "x = 17 mph in still water
\n" ); document.write( ":
\n" ); document.write( "Find y using equation: x + y = 24, substitute 17 for x
\n" ); document.write( "17 + y = 24
\n" ); document.write( "y = 24 - 17
\n" ); document.write( "y = 7 mph is the current
\n" ); document.write( ";
\n" ); document.write( ":
\n" ); document.write( "Check solution in the 2nd original equation: 6(x-y) = 60
\n" ); document.write( "6(17 - 7) = 60 \n" ); document.write( "
\n" );