document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=949510>Question 949510</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The current in a stream moves at a speed<BR>\n" );
document.write( "of 4 mph. A boat travels 5 mi upstream and 13 mi downstream<BR>\n" );
document.write( "in a total time of 2 hr. What is the speed of the<BR>\n" );
document.write( "boat in still water?\r<BR>\n" );
document.write( "\n" );
document.write( "I came up with zero for the speed in still water. Is that correct? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #579686 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=579686\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The current in a stream moves at a speed<BR>\n" );
document.write( " of 4 mph. A boat travels 5 mi upstream and 13 mi downstream<BR>\n" );
document.write( " in a total time of 2 hr. What is the speed of the<BR>\n" );
document.write( " boat in still water?<BR>\n" );
document.write( "---------------------<BR>\n" );
document.write( "upstream DATA:<BR>\n" );
document.write( "dist = 5 mi ; rate = b-4 mph ; time = d/r = 5/(b-4) hrs<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "Downstream DATA:<BR>\n" );
document.write( "dist = 13 mi ; rate = b+4 mph ; time = d/r = 13/(b+4) hrs<BR>\n" );
document.write( "------<BR>\n" );
document.write( "Equation:<BR>\n" );
document.write( "Total time = 2 hrs.<BR>\n" );
document.write( "5/(b-4) + 13/(b+4) = 2<BR>\n" );
document.write( "---<BR>\n" );
document.write( "5(b+4) + 13(b-4) = 2(b^2-16)<BR>\n" );
document.write( "18b - 32 = 2b^2 - 32<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "18b = 2b^2<BR>\n" );
document.write( "------<BR>\n" );
document.write( "b^2 - 9b = 0<BR>\n" );
document.write( "Factor:<BR>\n" );
document.write( "b(b-9) = 0<BR>\n" );
document.write( "=-----<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "boat speed = 9 mph<BR>\n" );
document.write( "=================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "---------------- <BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );