document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=132538>Question 132538</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Rita rows 12 km upstream and 12 km downstream in 3 hours. The speed of her boat in still water is 9 km/hr. Find the speed of the stream </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #96868 by </B><A HREF=/tutors/aboutme.mpl?userid=josmiceli><B>josmiceli(19441)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josmiceli><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=josmiceli><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=96868\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The key to these kind of problems is to spot<BR>\n" );
document.write( "the thing that doesn't change in the different<BR>\n" );
document.write( "instances given. In this case it's distance.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+r%2At ALIGN=MIDDLE  ALT=\"d+=+r%2At\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(rate going upstream) = (rate of boat in still water - rate of stream)<BR>\n" );
document.write( "(rate going downstream) = (rate of boat in still water + rate of stream)<BR>\n" );
document.write( "The combined time for both trips is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3 ALIGN=MIDDLE  ALT=\"3\"   DISABLED_style= \"max-width:90%; height:auto;\" > hours. This is<BR>\n" );
document.write( "separated into <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t ALIGN=MIDDLE  ALT=\"t\"   DISABLED_style= \"max-width:90%; height:auto;\" > anf <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3+-+t ALIGN=MIDDLE  ALT=\"3+-+t\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+%2B+s%29%2At ALIGN=MIDDLE  ALT=\"12+=+%289+%2B+s%29%2At\"   DISABLED_style= \"max-width:90%; height:auto;\" > (downstream)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+-+s%29%2A%283+-+t%29 ALIGN=MIDDLE  ALT=\"12+=+%289+-+s%29%2A%283+-+t%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > (upstream)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+12+%2F+%289+%2B+s%29 ALIGN=MIDDLE  ALT=\"t+=+12+%2F+%289+%2B+s%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+27+-+3s+-+9t+%2B+st ALIGN=MIDDLE  ALT=\"12+=+27+-+3s+-+9t+%2B+st\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "These are 2 equations and 2 unknowns, so should be solvable<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+27+-+3s+-+9%2A%2812%2F%289+%2B+s%29%29+%2B+s%2A%2812+%2F+%289+%2B+s%29%29 ALIGN=MIDDLE  ALT=\"12+=+27+-+3s+-+9%2A%2812%2F%289+%2B+s%29%29+%2B+s%2A%2812+%2F+%289+%2B+s%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "multiply both sides by <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9+%2B+s ALIGN=MIDDLE  ALT=\"9+%2B+s\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%2A%289+%2B+s%29+=+27%2A%289+%2B+s%29+-+3s%2A%289+%2B+s%29+-+108+%2B+12s ALIGN=MIDDLE  ALT=\"12%2A%289+%2B+s%29+=+27%2A%289+%2B+s%29+-+3s%2A%289+%2B+s%29+-+108+%2B+12s\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=108+%2B+12s+=+243+%2B+27s+-+27s+-+3s%5E2+-+108+%2B+12s ALIGN=MIDDLE  ALT=\"108+%2B+12s+=+243+%2B+27s+-+27s+-+3s%5E2+-+108+%2B+12s\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3s%5E2+%2B+216+-+243+=+0 ALIGN=MIDDLE  ALT=\"3s%5E2+%2B+216+-+243+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3s%5E2+-+27+=+0 ALIGN=MIDDLE  ALT=\"3s%5E2+-+27+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3s%5E2+=+27 ALIGN=MIDDLE  ALT=\"3s%5E2+=+27\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s%5E2+=+9 ALIGN=MIDDLE  ALT=\"s%5E2+=+9\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s+=+3 ALIGN=MIDDLE  ALT=\"s+=+3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The rate of the stream is 3 km/hr<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+%2B+s%29%2At ALIGN=MIDDLE  ALT=\"12+=+%289+%2B+s%29%2At\"   DISABLED_style= \"max-width:90%; height:auto;\" > (downstream)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+%2B+3%29%2At ALIGN=MIDDLE  ALT=\"12+=+%289+%2B+3%29%2At\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+12%2At ALIGN=MIDDLE  ALT=\"12+=+12%2At\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+1 ALIGN=MIDDLE  ALT=\"t+=+1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+-+s%29%2A%283+-+t%29 ALIGN=MIDDLE  ALT=\"12+=+%289+-+s%29%2A%283+-+t%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > (upstream)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+%289+-+3%29%2A%283+-+1%29 ALIGN=MIDDLE  ALT=\"12+=+%289+-+3%29%2A%283+-+1%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+6%2A2 ALIGN=MIDDLE  ALT=\"12+=+6%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12+=+12 ALIGN=MIDDLE  ALT=\"12+=+12\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "OK </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );