document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=134378>Question 134378</A>: <I><SPAN STYLE=\"word-break: break-all;\"> when lucy swims with the current, she swims 18km in 2 hours. against the current she can swim only 14km in the same time. how fast can lucy swim in still water? what is the rate of the current? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #98289 by </B><A HREF=/tutors/aboutme.mpl?userid=Earlsdon><B>Earlsdon(6294)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Earlsdon><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=98289\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Using the basic formula for distance, i.e. d = r*t where d = distance travelled, r = the rate of travel (speed), and t = the time taken to cover the distance, d. We can write two equations:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B1%5D+=+r%5B1%5Dt%5B1%5D ALIGN=MIDDLE  ALT=\"d%5B1%5D+=+r%5B1%5Dt%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > for Lucy's swim with the current.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B2%5D+=+r%5B2%5D%2At%5B2%5D ALIGN=MIDDLE  ALT=\"d%5B2%5D+=+r%5B2%5D%2At%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > for Lucy's swim against the current.<BR>\n" );
document.write( "We can express both <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D ALIGN=MIDDLE  ALT=\"r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D ALIGN=MIDDLE  ALT=\"r%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > in terms of the speed of the current (C) and in terms of Lucy's swimming speed in still water (R):<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+R%2BC ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+R%2BC\"   DISABLED_style= \"max-width:90%; height:auto;\" > Lucy's speed when swimming with the current is her speed in still water (R) plus the speed of the current (C).<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+R-C ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+R-C\"   DISABLED_style= \"max-width:90%; height:auto;\" > Lucy's speed when swimming against the current is her speed in still water (R) minus the speed of the current (C).<BR>\n" );
document.write( "For the first leg of the trip:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18+=+r%5B1%5D%2A2 ALIGN=MIDDLE  ALT=\"18+=+r%5B1%5D%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" > Substitute <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=R%2BC+=+r%5B1%5D ALIGN=MIDDLE  ALT=\"R%2BC+=+r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=18+=+%28R%2BC%29%2A2 ALIGN=MIDDLE  ALT=\"18+=+%28R%2BC%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 2.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9+=+R%2BC ALIGN=MIDDLE  ALT=\"9+=+R%2BC\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "For the second leg of the trip:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=14+=+r%5B2%5D%2A2 ALIGN=MIDDLE  ALT=\"14+=+r%5B2%5D%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" > Substitute <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=R-C+=+r%5B2%5D ALIGN=MIDDLE  ALT=\"R-C+=+r%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=14+=+%28R-C%29%2A2 ALIGN=MIDDLE  ALT=\"14+=+%28R-C%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 2.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7+=+R-C ALIGN=MIDDLE  ALT=\"7+=+R-C\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "So now you have two equations with two unknowns, R and C. Add these two equations to eliminate one of these variables (C):<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9+=+R%2BC ALIGN=MIDDLE  ALT=\"9+=+R%2BC\"   DISABLED_style= \"max-width:90%; height:auto;\" > Add these equations.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7+=+R-C ALIGN=MIDDLE  ALT=\"7+=+R-C\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "-------------<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=16+=+2R ALIGN=MIDDLE  ALT=\"16+=+2R\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 2.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=R+=+8 ALIGN=MIDDLE  ALT=\"R+=+8\"   DISABLED_style= \"max-width:90%; height:auto;\" >Km/hr. This is Lucy's speed in still water.<BR>\n" );
document.write( "Substitute this value of R into either one of the two equations we just added together:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9+=+R%2BC ALIGN=MIDDLE  ALT=\"9+=+R%2BC\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9+=+8%2BC ALIGN=MIDDLE  ALT=\"9+=+8%2BC\"   DISABLED_style= \"max-width:90%; height:auto;\" > Subtract 6 from both sides.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1+=+C ALIGN=MIDDLE  ALT=\"1+=+C\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=C+=+1 ALIGN=MIDDLE  ALT=\"C+=+1\"   DISABLED_style= \"max-width:90%; height:auto;\" >Km/hr.  This is the speed of the current. </SPAN>\n" );
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