document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=157872>Question 157872</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0131868462/algebrahomeworkh></A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A fisherman on the river rows 9 miles downstream in the same amount of time he rows 3 miles upstream.  if the current is 6 miles per hour. find how lonbg it takes him to cover the 12 miles. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #116356 by </B><A HREF=/tutors/aboutme.mpl?userid=nerdybill><B>nerdybill(7384)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=nerdybill><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=nerdybill><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=116356\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">     A fisherman on the river rows 9 miles downstream in the same amount of time he rows 3 miles upstream. if the current is 6 miles per hour. find how lonbg it takes him to cover the 12 miles.<BR>\n" );
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document.write( "Apply the distance formula:<BR>\n" );
document.write( "d = rt<BR>\n" );
document.write( "where<BR>\n" );
document.write( "d is distance<BR>\n" );
document.write( "r is rate or speed<BR>\n" );
document.write( "t is time<BR>\n" );
document.write( ".<BR>\n" );
document.write( "solving for t we get:<BR>\n" );
document.write( "t = d/r<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Let f = speed of boat in still water<BR>\n" );
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document.write( "9/(f+6) = 3/(f-6)<BR>\n" );
document.write( "cross multiplying we get:<BR>\n" );
document.write( "3(f+6) = 9(f-6)<BR>\n" );
document.write( "3f + 18 = 9f - 54<BR>\n" );
document.write( "18 = 6f - 54<BR>\n" );
document.write( "72 = 6f<BR>\n" );
document.write( "12 mph = f (speed of boat in still water)<BR>\n" );
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document.write( "Time traveling downstream:<BR>\n" );
document.write( "t = 9/(f+6)<BR>\n" );
document.write( "t = 9/(12+6)<BR>\n" );
document.write( "t = 9/18<BR>\n" );
document.write( "t = 1/2 hour<BR>\n" );
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document.write( "Time traveling upstream:<BR>\n" );
document.write( "t = 3/(f-6)<BR>\n" );
document.write( "t = 3/(12-6)<BR>\n" );
document.write( "t = 3/18<BR>\n" );
document.write( "t = 1/6<BR>\n" );
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document.write( "Total time:<BR>\n" );
document.write( "1/2 + 1/6 = 3/6 + 1/6 = 4/6 = 2/3 hours<BR>\n" );
document.write( "or, in terms of minutes<BR>\n" );
document.write( "2/3 * 60 = 2 * 20 = 40 minutes\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );