document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=848814>Question 848814</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In still water, a boat averages 18 miles per hour. In a river, it takes the same amount of time to travel 33 miles downstream as it takes to travel 21 miles upstream. What is the rate of the rivers current? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #511274 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39623)</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=511274\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> c = speed of the river current<BR>\n" );
document.write( "t = the same amount of time for the up and down streams distances<BR>\n" );
document.write( "18 = boat speed when not in any current\r<BR>\n" );
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document.write( "Model uniform rate equation for travel is R*T=D, Rate, Time, Distance.\r<BR>\n" );
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document.write( "__________________speed__________time___________distances<BR>\n" );
document.write( "downstream________18+c___________t______________33<BR>\n" );
document.write( "upstream__________18-c___________t______________21\r<BR>\n" );
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document.write( "The downstream equation is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2818%2Bc%29t=33 ALIGN=MIDDLE  ALT=\"%2818%2Bc%29t=33\"   DISABLED_style= \"max-width:90%; height:auto;\" >;<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18t%2Bct=33 ALIGN=MIDDLE  ALT=\"18t%2Bct=33\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "the upstream equation is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2818-c%29t=21 ALIGN=MIDDLE  ALT=\"%2818-c%29t=21\"   DISABLED_style= \"max-width:90%; height:auto;\" >;<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18t-ct=21 ALIGN=MIDDLE  ALT=\"18t-ct=21\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
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document.write( "Two nonlinear equations in two unknowns c and t.  The situation in the example allows for the elimination method for the term <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight_green%28ct%29 ALIGN=MIDDLE  ALT=\"highlight_green%28ct%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Add the left members and equate to the addition of the right-side members.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18t%2Bct%2B18t-ct=33%2B21 ALIGN=MIDDLE  ALT=\"18t%2Bct%2B18t-ct=33%2B21\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=36t%2B0=54 ALIGN=MIDDLE  ALT=\"36t%2B0=54\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=54%2F36 ALIGN=MIDDLE  ALT=\"t=54%2F36\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=3%2A3%2A3%2A2%2F%286%2A6%29=%283%2A3%2A3%2A2%29%2F%282%2A3%2A2%2A3%29=%283%2A2%29%2F%282%2A2%29=3%2F2 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28t=%283%2F2%29%29 ALIGN=MIDDLE  ALT=\"highlight%28t=%283%2F2%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "The question is for the speed of the current, c.<BR>\n" );
document.write( "Solve either travel equation for c and then use the now found t to compute c.<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18t-ct=21 ALIGN=MIDDLE  ALT=\"18t-ct=21\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-ct=21-18t ALIGN=MIDDLE  ALT=\"-ct=21-18t\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=c=%2821-18t%29%2F%28-t%29 ALIGN=MIDDLE  ALT=\"c=%2821-18t%29%2F%28-t%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%28highlight%28c=%2818t-21%29%2Ft%29%29 ALIGN=MIDDLE  ALT=\"highlight%28highlight%28c=%2818t-21%29%2Ft%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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