document.write( "Question 861850: Manny can paddle his canoe at a rate of 7 miles per hour in still water. he travels 45 miles upstream and 45 miles downstream in a total time of 14 hours. what is the speed of the current? \n" ); document.write( "

Algebra.Com's Answer #519350 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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Manny can paddle his canoe at a rate of 7 miles per hour in still water. he travels 45 miles upstream and 45 miles downstream in a total time of 14 hours. what is the speed of the current?
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\n" ); document.write( "let c = rate of the current
\n" ); document.write( "then
\n" ); document.write( "(7+c) = effective speed down stream
\n" ); document.write( "and
\n" ); document.write( "(7-c) = effective speed up stream
\n" ); document.write( ":
\n" ); document.write( "Write a time equation, time = dist/speed
\n" ); document.write( "time down + time up = 14 hrs
\n" ); document.write( " $\"45%2F%28%287%2Bc%29%29\"$ + $\"45%2F%28%287-c%29%29\"$ = 14
\n" ); document.write( "multiply equation by (7+c)(7-c), resulting in
\n" ); document.write( "45(7-c) + 45(7+c) = 14(7-c)(7+c)
\n" ); document.write( "315 - 45c + 315 + 45c = 14(49 - c^2)
\n" ); document.write( "630 = 686 - 14c^2
\n" ); document.write( "14c^2 = 686 - 630
\n" ); document.write( "14c^2 = 56
\n" ); document.write( "c^2 = 56/14
\n" ); document.write( "c^2 = 4
\n" ); document.write( "c = $\"sqrt%284%29\"$
\n" ); document.write( "c = 2 km/h is the current
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check this, find the time each way
\n" ); document.write( "45/9 = 5
\n" ); document.write( "45/5 = 9
\n" ); document.write( "--------
\n" ); document.write( "total: 14 hrs \n" ); document.write( "

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