document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=679635>Question 679635</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Chance paddled a canoe 10 miles upstream in a river that has a current of 4 mph. He then turned around and paddled downstream until he reached his original starting place. If the entire trip took him 7 hours, how fast would Chance paddle in still water? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #421997 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=421997\">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=+s+ ALIGN=MIDDLE  ALT=\"+s+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = the speed of the boat in still water<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+%2B+4+ ALIGN=MIDDLE  ALT=\"+s+%2B+4+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = speed of canoe going downstream<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+-+4+ ALIGN=MIDDLE  ALT=\"+s+-+4+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = speed of canoe going upstream<BR>\n" );
document.write( "Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+ ALIGN=MIDDLE  ALT=\"+t+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = time to go upstream<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+7+-+t+ ALIGN=MIDDLE  ALT=\"+7+-+t+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = time to go downstream<BR>\n" );
document.write( "------------------<BR>\n" );
document.write( "Equation for going upstream:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+s+-+4+%29%2At+ ALIGN=MIDDLE  ALT=\"+10+=+%28+s+-+4+%29%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Equation for going downstream:<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+s+%2B+4+%29%2A%28+7+-+t+%29+ ALIGN=MIDDLE  ALT=\"+10+=+%28+s+%2B+4+%29%2A%28+7+-+t+%29+\"   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=+t+=+10+%2F+%28+s+-+4+%29+ ALIGN=MIDDLE  ALT=\"+t+=+10+%2F+%28+s+-+4+%29+\"   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=+10+=+7s+%2B+28+-+s%2At+-+4t+ ALIGN=MIDDLE  ALT=\"+10+=+7s+%2B+28+-+s%2At+-+4t+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+7s+%2B+28+-+t%2A%28+s+%2B+4+%29+ ALIGN=MIDDLE  ALT=\"+10+=+7s+%2B+28+-+t%2A%28+s+%2B+4+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Substitute (1) into (2)<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+7s+%2B+28+-+%28+10+%2F+%28+s+-+4+%29+%29%2A%28+s+%2B+4+%29+ ALIGN=MIDDLE  ALT=\"+10+=+7s+%2B+28+-+%28+10+%2F+%28+s+-+4+%29+%29%2A%28+s+%2B+4+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+7s+%2B+18+=+++%28+10+%2F+%28+s+-+4+%29+%29%2A%28+s+%2B+4+%29+ ALIGN=MIDDLE  ALT=\"+7s+%2B+18+=+++%28+10+%2F+%28+s+-+4+%29+%29%2A%28+s+%2B+4+%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=+s+-+4+ ALIGN=MIDDLE  ALT=\"+s+-+4+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+%28+s+-+4+%29%2A%28+7s+%2B+18+%29+=+10s+%2B+40+ ALIGN=MIDDLE  ALT=\"+%28+s+-+4+%29%2A%28+7s+%2B+18+%29+=+10s+%2B+40+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+7s%5E2+-+28s+%2B+18s+-+72+=+10s+%2B+40+ ALIGN=MIDDLE  ALT=\"+7s%5E2+-+28s+%2B+18s+-+72+=+10s+%2B+40+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+7s%5E2+-+20s+-112+=+0+ ALIGN=MIDDLE  ALT=\"+7s%5E2+-+20s+-112+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Use quadratic formula<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+%28+-b+%2B-+sqrt%28+b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29+ ALIGN=MIDDLE  ALT=\"+s+=+%28+-b+%2B-+sqrt%28+b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+=+7+ ALIGN=MIDDLE  ALT=\"+a+=+7+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+=+-20+ ALIGN=MIDDLE  ALT=\"+b+=+-20+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+c+=+-112+ ALIGN=MIDDLE  ALT=\"+c+=+-112+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+%28+-%28-20%29+%2B-+sqrt%28+%28-20%29%5E2+-+4%2A7%2A%28-112%29+%29%29+%2F+%282%2A7%29+ ALIGN=MIDDLE  ALT=\"+s+=+%28+-%28-20%29+%2B-+sqrt%28+%28-20%29%5E2+-+4%2A7%2A%28-112%29+%29%29+%2F+%282%2A7%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+%28+20+%2B-+sqrt%28+400+%2B+3136+%29%29+%2F+14+ ALIGN=MIDDLE  ALT=\"+s+=+%28+20+%2B-+sqrt%28+400+%2B+3136+%29%29+%2F+14+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+%28+20+%2B+sqrt%28+3536+%29%29+%2F+14+ ALIGN=MIDDLE  ALT=\"+s+=+%28+20+%2B+sqrt%28+3536+%29%29+%2F+14+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+%28+20+%2B+59.464+%29+%2F+14+ ALIGN=MIDDLE  ALT=\"+s+=+%28+20+%2B+59.464+%29+%2F+14+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+79.464+%2F+14+ ALIGN=MIDDLE  ALT=\"+s+=+79.464+%2F+14+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+5.676+ ALIGN=MIDDLE  ALT=\"+s+=+5.676+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The speed in still water is 5.676 mi/hr<BR>\n" );
document.write( "check answer:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+s+-+4+%29%2At+ ALIGN=MIDDLE  ALT=\"+10+=+%28+s+-+4+%29%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+5.676+-+4+%29%2At+ ALIGN=MIDDLE  ALT=\"+10+=+%28+5.676+-+4+%29%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+1.676%2At+ ALIGN=MIDDLE  ALT=\"+10+=+1.676%2At+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t+=+5.967+ ALIGN=MIDDLE  ALT=\"+t+=+5.967+\"   DISABLED_style= \"max-width:90%; height:auto;\" > hrs<BR>\n" );
document.write( "-------------------<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+s+%2B+4+%29%2A%28+7+-+5.967+%29+ ALIGN=MIDDLE  ALT=\"+10+=+%28+s+%2B+4+%29%2A%28+7+-+5.967+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+10+=+%28+s+%2B+4+%29%2A1.033+ ALIGN=MIDDLE  ALT=\"+10+=+%28+s+%2B+4+%29%2A1.033+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+9.681+=+s+%2B+4+ ALIGN=MIDDLE  ALT=\"+9.681+=+s+%2B+4+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+5.681+ ALIGN=MIDDLE  ALT=\"+s+=+5.681+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "----------------<BR>\n" );
document.write( "This is pretty close. Error could be<BR>\n" );
document.write( "due to rounding off. I think the method<BR>\n" );
document.write( "is correct anyway.\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );