document.write( "Question 209211: Julie and Eric row their boat (at a constant speed) 45 miles downstream for 5 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current. \n" ); document.write( "
Algebra.Com's Answer #158155 by nerdybill(7384)\"\" \"About 
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Julie and Eric row their boat (at a constant speed) 45 miles downstream for 5 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current.
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\n" ); document.write( "You will need to apply the \"distance formula\":
\n" ); document.write( "d = rt
\n" ); document.write( "where
\n" ); document.write( "d is distance
\n" ); document.write( "r is rate or speed
\n" ); document.write( "t is time
\n" ); document.write( ".
\n" ); document.write( "Let x = rate of the current
\n" ); document.write( "and y = rate Julie and Eric can row
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\n" ); document.write( "Since we have two variables, we'll need two equations:
\n" ); document.write( "Downstream:
\n" ); document.write( "5(y+x) = 45 (equation 1)
\n" ); document.write( "Upstream:
\n" ); document.write( "9(y-x) = 45 (equation 2)
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\n" ); document.write( "Solve equation 2 for y:
\n" ); document.write( "9(y-x) = 45
\n" ); document.write( "y-x = 5
\n" ); document.write( "y = 5+x
\n" ); document.write( ".
\n" ); document.write( "Substitute the above into equation 1 and solve for x:
\n" ); document.write( "5(y+x) = 45
\n" ); document.write( "5(5+x+x) = 45
\n" ); document.write( "5+x+x = 9
\n" ); document.write( "2x = 4
\n" ); document.write( "x = 2 mph (rate of the current)
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