document.write( "Question 1129775: A boat went 8 kilometers upstream and returned all in 2 hours. If the current was running at 3km/hr, what is the boat’s speed in still water? \n" ); document.write( "

Algebra.Com's Answer #746395 by ikleyn(52943) $\"\"$ $\"About$

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document.write( "Let x be the boat speed in still water, in km/h.\r\n" );
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document.write( "Then your \"time\" equation is\r\n" );
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document.write( " +  = 2   hours.\r\n" );
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document.write( "8*(x+3) + 8*(x-3) = 2*(x+3)*(x-3)\r\n" );
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document.write( "8x + 24 + 8x - 24 = 2*(x^2-9)\r\n" );
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document.write( "16x = 2x^2 - 18\r\n" );
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document.write( "2x^2 - 16x - 18 = 0\r\n" );
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document.write( "x^2 - 8x - 9 = 0\r\n" );
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document.write( " =  =  = .\r\n" );
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document.write( "Only positive root  x =  = 9 km/h  is meaningful. \r\n" );
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document.write( "Check.   +  =  =  =  = 2  hours.   ! Correct !\r\n" );
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document.write( "Answer.   The speed of the boat in still water is 9 km/h.\r\n" );
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\n" ); document.write( "\n" ); document.write( "It is a typical and standard Upstream and Downstream round trip word problem.\r
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\n" ); document.write( "\n" ); document.write( "You can find many similar fully solved problems on upstream and downstream round trips with detailed solutions in lessons \r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems \r
\n" ); document.write( "\n" ); document.write( "    - More problems on upstream and downstream round trips \r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems solvable by quadratic equations \r
\n" ); document.write( "\n" ); document.write( "    - Unpowered raft floating downstream along a river\r
\n" ); document.write( "\n" ); document.write( "    - Selected problems from the archive on the boat floating Upstream and Downstream \r
\n" ); document.write( "\n" ); document.write( "in this site, where you will find other similar solved problems with detailed explanations.\r
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\n" ); document.write( "\n" ); document.write( "Read them attentively and learn how to solve this type of problems once and for all.\r
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\n" ); document.write( "\n" ); document.write( "Also, you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this textbook under the section \"Word problems\", the topic \"Travel and Distance problems\".\r
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\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Save the link to this online textbook together with its description\r
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\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-I
\n" ); document.write( "https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson\r
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\n" ); document.write( "\n" ); document.write( "to your archive and use it when it is needed.\r
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