document.write( "Question 1089552: Julie and Eric row their boat (at a constant speed) 63 miles downstream for 7 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current. \n" ); document.write( "

Algebra.Com's Answer #703891 by ikleyn(52781) $\"\"$ $\"About$

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\n" ); document.write( "Julie and Eric row their boat (at a constant speed) 63 miles downstream for 7 hours, helped by the current.
\n" ); document.write( "Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current.
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document.write( "Let u be the rate of the boat in a still water (at no current), in miles per hour.\r\n" );
document.write( "Let v be the rate of the stream.\r\n" );
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document.write( "Then the rate rowing downstream is (u+v) relative to the river banks.\r\n" );
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document.write( "From the other side, this rate is  = 9 mph, according to the condition, \r\n" );
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document.write( "It gives you your first equation\r\n" );
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document.write( "u + v = 9.    \r\n" );
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document.write( "The rate rowing upstream is (u-v) relative to the river banks.\r\n" );
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document.write( "From the other side, this rate is  = 7 mph, according to the condition, \r\n" );
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document.write( "It gives you your second equation\r\n" );
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document.write( "u - v = 9.    \r\n" );
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document.write( "Combining equations (1) and (2) together, you get the system of two equations\r\n" );
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document.write( "u + v = 9,     (1)\r\n" );
document.write( "u - v = 7.     (2)\r\n" );
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document.write( "To solve the system, add the equations (1) and (2). You will get\r\n" );
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document.write( "2u = 9 + 7 = 16  ====>  u =  = 8.\r\n" );
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document.write( "Thus you found that the rate of the boat in the still water is 8 miles per hour.\r\n" );
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document.write( "Then from (1), v = 9 - u = 9 - 8 = 1 mph.\r\n" );
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document.write( "Answer.  The rate of the current is 1 mile per hour.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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\n" ); document.write( "\n" ); document.write( "It is a typical and standard Upstream and Downstream round trip word problem.\r
\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
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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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