document.write( "Question 783632: A speedboat can travel at 20km per hour in still water. It takes the boat 3/5 as much time to travel 90km down river as it does to travel the same distance up river. Find the rate of the river current in kilometers per hour. \n" ); document.write( "
Algebra.Com's Answer #476876 by ankor@dixie-net.com(22740)\"\" \"About 
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A speedboat can travel at 20km per hour in still water.
\n" ); document.write( " It takes the boat 3/5 as much time to travel 90km down river as it does to travel the same distance up river.
\n" ); document.write( " Find the rate of the river current in kilometers per hour.
\n" ); document.write( ":
\n" ); document.write( "Actually we can do this without knowing the distance. Use .6 for 3/5
\n" ); document.write( "Let r = rate of the river
\n" ); document.write( "then
\n" ); document.write( "(20-r) = effective speed up-river
\n" ); document.write( "and
\n" ); document.write( "(20+r) = effective speed down river
\n" ); document.write( ":
\n" ); document.write( "Write a distance equation, dist = time * speed
\n" ); document.write( ".6(20+r) = 1(20-r)
\n" ); document.write( "12 + .6r = 20 - r
\n" ); document.write( ".6r + r = 20 - 12
\n" ); document.write( "1.6r = 8
\n" ); document.write( "r = 8/1.6
\n" ); document.write( "r = 5 km/hr is the rate of the current \n" ); document.write( "
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