document.write( "Question 182476: Fred paddled for 5 hours with 7km/hr current to reach a campsite. The return trip against the same current took 10 hours. Find the speed of Fred's canoe in still water? \n" ); document.write( "
Algebra.Com's Answer #136949 by Alan3354(69443)\"\" \"About 
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Fred paddled for 5 hours with 7km/hr current to reach a campsite. The return trip against the same current took 10 hours. Find the speed of Fred's canoe in still water?
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\n" ); document.write( "He traveled the same distance, s km.
\n" ); document.write( "Call the canoe speed c, to save typing.
\n" ); document.write( "The time is the distance/rate
\n" ); document.write( "Going downstream, his rate (r) was c+7
\n" ); document.write( "Going upstream, his rate was c-7
\n" ); document.write( "The time downstream, 5 hrs = s/(c+7)
\n" ); document.write( "The time upstream, 10 hrs = s/(c-7)
\n" ); document.write( "Now there are 2 equations in 2 unknowns, so we're home free. Almost.
\n" ); document.write( "5 hrs = s/(c+7)
\n" ); document.write( "10 hrs = s/(c-7)
\n" ); document.write( "s = 5(c+7) = 5c+35
\n" ); document.write( "s = 10(c-7) = 10c-70
\n" ); document.write( "Since they both equal s, they equal each other
\n" ); document.write( "5c+35 = 10c-70
\n" ); document.write( "5c = 105
\n" ); document.write( "c = 21 km/hr (the speed of the canoe)
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\n" ); document.write( "Tho it wasn't asked for, the distance is 140 kms. Going 21km/hr (12.6 mph) for 140 km is stepping right along. I'd check for a motor or steroids.\r
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