document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=807766>Question 807766</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A thee hour river cruise goes 15km upstream and then back again. The river has a current of 2km an hour. What is the boat's speed and how long was the upstream journey? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #486517 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39616)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=486517\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> r = boat speed if no current present.<BR>\n" );
document.write( "c = 2 km/h current of river.<BR>\n" );
document.write( "u = time going upstream<BR>\n" );
document.write( "3-u = time going downstream (based on description and on assignment of u)\r<BR>\n" );
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document.write( "________________speed____________time___________distance(km)<BR>\n" );
document.write( "Upstream________r-c______________(u)__________(___)<BR>\n" );
document.write( "Downstream______r+c______________(3-u)__________(___)<BR>\n" );
document.write( "Total______________________________3_____________15\r<BR>\n" );
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document.write( "Two unknown variables ,  r and u.  Filling in the distance data,\r<BR>\n" );
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document.write( "________________speed____________time___________distance(km)<BR>\n" );
document.write( "Upstream________r-c______________(u)__________((r-c)(u))<BR>\n" );
document.write( "Downstream______r+c______________(3-u)__________((r+c)(3-u))<BR>\n" );
document.write( "Total______________________________3_____________15\r<BR>\n" );
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document.write( "The \"Total\" data gives an equation:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28r-c%29%28u%29%2B%28r%2Bc%29%283-u%29=15 ALIGN=MIDDLE  ALT=\"%28r-c%29%28u%29%2B%28r%2Bc%29%283-u%29=15\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "'<BR>\n" );
document.write( "Steps<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ru-rc%2B3r%2B3c-ur-uc=15 ALIGN=MIDDLE  ALT=\"ru-rc%2B3r%2B3c-ur-uc=15\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ru-rc%2B3r-r%2B3c-uc=15 ALIGN=MIDDLE  ALT=\"ru-rc%2B3r-r%2B3c-uc=15\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%28u-c%2B3-1%29%2B3c-uc=15 ALIGN=MIDDLE  ALT=\"r%28u-c%2B3-1%29%2B3c-uc=15\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%28u-c%2B2%29=15%2Buc-3c ALIGN=MIDDLE  ALT=\"r%28u-c%2B2%29=15%2Buc-3c\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r=%2815%2Buc-3c%29%2F%28u-c%2B2%29 ALIGN=MIDDLE  ALT=\"r=%2815%2Buc-3c%29%2F%28u-c%2B2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Substituting for c=2,<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r=%2815%2B2u-6%29%2F%28u%29 ALIGN=MIDDLE  ALT=\"r=%2815%2B2u-6%29%2F%28u%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28r=%289%2B2u%29%2Fu%29 ALIGN=MIDDLE  ALT=\"highlight%28r=%289%2B2u%29%2Fu%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > This is still one equation in TWO unknown variables.\r<BR>\n" );
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document.write( "This will have infinite solutions but there is a restriction.  <BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%280%3Cu%3C3%29 ALIGN=MIDDLE  ALT=\"highlight%280%3Cu%3C3%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >  is that restriction.  You may compute r accordingly for its RANGE.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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