document.write( "Question 205995: 1- In a river that flows at 3 mph, a boat takes 1 hour longer to sail 36 miles upstream than to return. Find the speed of the boat in still water.
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Algebra.Com's Answer #155601 by ankor@dixie-net.com(22740)\"\" \"About 
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In a river that flows at 3 mph, a boat takes 1 hour longer to sail 36 miles
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\n" ); document.write( " Find the speed of the boat in still water.
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\n" ); document.write( "Let s = speed of boat in still water
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\n" ); document.write( "(s+3) = speed downstream
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\n" ); document.write( "(s-3) = speed upstream
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\n" ); document.write( "Write a time equation
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\n" ); document.write( "time downstream = time upstream - 1 hr
\n" ); document.write( "\"36%2F%28%28s%2B3%29%29\" = \"36%2F%28%28s-3%29%29\" - 1
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\n" ); document.write( "Multiply equation by (s+3)(s-3), results
\n" ); document.write( "36(s-3) = 36(s+3) - (s+3)(s-3)(1)
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\n" ); document.write( "36s - 108 = 36s + 108 - (s^2 - 9)
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\n" ); document.write( "36s - 108 = 36s + 108 - s^2 + 9
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\n" ); document.write( "Combine like terms on the left:
\n" ); document.write( "s^2 + 36s - 36s - 108 - 108 - 9 = 0
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\n" ); document.write( " s^2 - 225 = 0
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\n" ); document.write( "s^2 = 225
\n" ); document.write( "s = \"sqrt%28225%29\"
\n" ); document.write( "s = 15 mph, speed in still water
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\n" ); document.write( "Check solution by finding the times
\n" ); document.write( "36/(15-3) = 3 hrs
\n" ); document.write( "36/(15+3) = 2 hrs
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\n" ); document.write( "differs by: 1 hr
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