document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=40797>Question 40797</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0536965943/algebrahomeworkh>Beginning Algebra</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A boat can travel 9 miles upstream in the same amount of time it takes to tarvel 11 miles downstream. If the current of the river is 3miles per hour, complete the chart below and use it to find the speed of the boat in still water.<BR>\n" );
document.write( "         distance  =  rate   *   time<BR>\n" );
document.write( "UPSTREAM   9          r-3<BR>\n" );
document.write( "DOWNSTREAM 11         r+3 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #26191 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=26191\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> r = rate of boat in still water<BR>\n" );
document.write( "t = time for both trips<BR>\n" );
document.write( "For upstream<BR>\n" );
document.write( "9 = (r-3)t<BR>\n" );
document.write( "for downstream<BR>\n" );
document.write( "11 = (r+3)t<BR>\n" );
document.write( "solve each for r<BR>\n" );
document.write( "r-3 = 9/t<BR>\n" );
document.write( "r = 9/t + 3<BR>\n" );
document.write( "--------------<BR>\n" );
document.write( "r+3 = 11/t<BR>\n" );
document.write( "r = 11/t - 3<BR>\n" );
document.write( "I'll plot these equations, t on the horizontal axis, r on the vertical.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+500%2C+300%2C+-.5%2C+2%2C+-2%2C+32%2C+9%2Fx+%2B3%2C+11%2Fx+-+3%29+ ALIGN=MIDDLE  ALT=\"+graph%28+500%2C+300%2C+-.5%2C+2%2C+-2%2C+32%2C+9%2Fx+%2B3%2C+11%2Fx+-+3%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "It looks like the times are equal when r is about 30 mph, the rate of<BR>\n" );
document.write( "boat in still water.<BR>\n" );
document.write( "check<BR>\n" );
document.write( "r = 9/t + 3<BR>\n" );
document.write( "r = 11/t - 3<BR>\n" );
document.write( "30 = 9/t + 3<BR>\n" );
document.write( "27 = 9/t<BR>\n" );
document.write( "27t = 9<BR>\n" );
document.write( "t = 1/3 hr<BR>\n" );
document.write( "-------------<BR>\n" );
document.write( "30 = 11/t - 3<BR>\n" );
document.write( "33 = 11/t<BR>\n" );
document.write( "33t = 11<BR>\n" );
document.write( "t = 1/3 hr<BR>\n" );
document.write( "OK </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );