document.write( "Question 422234: Jan and Tariq took a canoeing trip, traveling 6 mi upstream against a 2 mi/h current. They then returned to the same point downstream. If their entire trip took 4 h, how fast can they paddle in still water? [Hint: If r is their rate (in miles per hour) in still water, their rate upstream is r - 2 and their rate downstream is r + 2.]
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Algebra.Com's Answer #294746 by mananth(16946)\"\" \"About 
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speed in still water = r
\n" ); document.write( "current speed 2
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\n" ); document.write( "upstream speed = r-2
\n" ); document.write( "downstream speed = r+2
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\n" ); document.write( "Distance= 6 miles
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\n" ); document.write( "Time upstream + time downstream = 4 hours
\n" ); document.write( "t=d/r \r
\n" ); document.write( "\n" ); document.write( "6/(r+2)+ 6/(r-2)= 4
\n" ); document.write( "LCD =(r- 2)(r+2)
\n" ); document.write( "6*(r-2) +6(r+2)= 4
\n" ); document.write( "6r-12+6r +12=4(r^2-4)
\n" ); document.write( "12r=4r^2 -16
\n" ); document.write( "4r^2-12r -16=0
\n" ); document.write( "4(r^2-3r-4)=0
\n" ); document.write( "(r^2-3r-4)=0
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\n" ); document.write( "Find the roots of the equation by quadratic formula
\n" ); document.write( "a= 1 , b = -3 , c = -4 .
\n" ); document.write( "b^2-4ac= 25
\n" ); document.write( "\"x1=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"
\n" ); document.write( "\"x1=%283%2Bsqrt%2825%29%29%2F2\"
\n" ); document.write( "x1=4
\n" ); document.write( "\"x2=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"
\n" ); document.write( "\"x2=%283-sqrt%2825%29%29%2F2\"
\n" ); document.write( "x2=-1 ( this is negative so not possible)
\n" ); document.write( "The speed of paddling in still water = 4 mph
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