document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=299982>Question 299982</A>: <I><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "A motorboat takes 4 hours to travel 320 mi going upstream. The return trip takes  hours 2 going downstream. What is the rate of the boat in still water and 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 #215370 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=215370\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bs%5D ALIGN=MIDDLE  ALT=\"r%5Bs%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > = rate of boat in still water<BR>\n" );
document.write( "Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bc%5D ALIGN=MIDDLE  ALT=\"r%5Bc%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > = rate of the current<BR>\n" );
document.write( "Write 2 equations, one for upstream and one for downstream<BR>\n" );
document.write( "given:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5Bu%5D+=+4 ALIGN=MIDDLE  ALT=\"t%5Bu%5D+=+4\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5Bd%5D+=+2 ALIGN=MIDDLE  ALT=\"t%5Bd%5D+=+2\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d=+320 ALIGN=MIDDLE  ALT=\"d=+320\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi<BR>\n" );
document.write( "-----------<BR>\n" );
document.write( "upstream:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+r%5Bu%5D%2At%5Bu%5D ALIGN=MIDDLE  ALT=\"d+=+r%5Bu%5D%2At%5Bu%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2At%5Bu%5D ALIGN=MIDDLE  ALT=\"d+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2At%5Bu%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4 ALIGN=MIDDLE  ALT=\"320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "downstream:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+r%5Bd%5D%2At%5Bd%5D ALIGN=MIDDLE  ALT=\"d+=+r%5Bd%5D%2At%5Bd%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2At%5Bd%5D ALIGN=MIDDLE  ALT=\"d+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2At%5Bd%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2 ALIGN=MIDDLE  ALT=\"320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "-----------------<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bs%5D+-+r%5Bc%5D+=+80 ALIGN=MIDDLE  ALT=\"r%5Bs%5D+-+r%5Bc%5D+=+80\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bs%5D+%2B+r%5Bc%5D+=+160 ALIGN=MIDDLE  ALT=\"r%5Bs%5D+%2B+r%5Bc%5D+=+160\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Add the equations<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2r%5Bs%5D+=+240 ALIGN=MIDDLE  ALT=\"2r%5Bs%5D+=+240\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bs%5D+=+120 ALIGN=MIDDLE  ALT=\"r%5Bs%5D+=+120\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi/hr<BR>\n" );
document.write( "And, since<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bs%5D+-+r%5Bc%5D+=+80 ALIGN=MIDDLE  ALT=\"r%5Bs%5D+-+r%5Bc%5D+=+80\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=120+-+r%5Bc%5D+=+80 ALIGN=MIDDLE  ALT=\"120+-+r%5Bc%5D+=+80\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5Bc%5D+=+40 ALIGN=MIDDLE  ALT=\"r%5Bc%5D+=+40\"   DISABLED_style= \"max-width:90%; height:auto;\" > mi/hr<BR>\n" );
document.write( "The rate of the boat in still water is120 mi/hr<BR>\n" );
document.write( "The rate of the current is 40 mi/hr<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4 ALIGN=MIDDLE  ALT=\"320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28120+-+40%29%2A4 ALIGN=MIDDLE  ALT=\"320+=+%28120+-+40%29%2A4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+320 ALIGN=MIDDLE  ALT=\"320+=+320\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2 ALIGN=MIDDLE  ALT=\"320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+%28120+%2B+40%29%2A2 ALIGN=MIDDLE  ALT=\"320+=+%28120+%2B+40%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=320+=+320 ALIGN=MIDDLE  ALT=\"320+=+320\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "OK </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );