document.write( "Question 326281: sammy owns a motor boat that travels 4 miles/hour in still water. It goes 12 miles upstream and 12 miles back again (downstream) in a total of 8 hours. Find the speed of the current of the river. \n" ); document.write( "

Algebra.Com's Answer #233577 by mananth(16946) $\"\"$ $\"About$

You can put this solution on YOUR website!
still water speed = 4mph
\n" ); document.write( "let speed of current be xmph
\n" ); document.write( "..
\n" ); document.write( "upstream speed = x-4 mph
\n" ); document.write( "distance traveled = 12 miles
\n" ); document.write( "time taken = 12/x-4
\n" ); document.write( "..
\n" ); document.write( "down stream speed = x+4 mph
\n" ); document.write( "distance traveled = 12 miles
\n" ); document.write( "time taken = x+4 /12 ..
\n" ); document.write( "time upstream + time down stream = total time up and down
\n" ); document.write( "..
\n" ); document.write( " $\"12%2F%28x-4%29%2B12%2F%28x%2B4%29=8\"$
\n" ); document.write( "LCM of left side = (x+4)(x-4)
\n" ); document.write( " $\"%2812%28x%2B4%29%2B12%28x-4%29%29%2F%28x%2B4%29%28x-4%29=8\"$
\n" ); document.write( " $\"12x%2B48%2B12x-48=8%28x%5E2-4%29\"$
\n" ); document.write( " $\"24x=8x%5E2-32\"$
\n" ); document.write( "Add-24x to both sides
\n" ); document.write( " $\"8x%5E2-24x-32=0\"$
\n" ); document.write( " $\"8%28x%5E2-3x-4%29=0\"$
\n" ); document.write( " $\"x%5E2-3x-4=0\"$
\n" ); document.write( " $\"%28x-4%29%28x%2B1%29=0\"$
\n" ); document.write( "x=4 Or -1
\n" ); document.write( "ignore -1
\n" ); document.write( "speed of current = 4 mph \n" ); document.write( "

\n" );