document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=212693>Question 212693</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/9780495013570/algebrahomeworkh></A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> distance,speed, and time.<BR>\n" );
document.write( "It took a crew 2 hours and 40mins. to row 6km upstream and back again. If the rate of flow of the stream was 3km/hr, what was the rowing speed of the crew 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 #160604 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=160604\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> distance,speed, and time.<BR>\n" );
document.write( "It took a crew 2 hours and 40mins. to row 6km upstream and back again. If the rate of flow of the stream was 3km/hr, what was the rowing speed of the crew in still water?<BR>\n" );
document.write( "------------------------<BR>\n" );
document.write( "Upstream DATA:<BR>\n" );
document.write( "distance = 6 km ; rate = b-3 km ; time = 6/(b-3) hrs<BR>\n" );
document.write( "----------------------------<BR>\n" );
document.write( "Downstream DATA:<BR>\n" );
document.write( "distance = 6 km ; rate = b+3 km ; time = 6/(b+3) hrs<BR>\n" );
document.write( "-------------------------------<BR>\n" );
document.write( "Equation:<BR>\n" );
document.write( "time + time = 2 2/3 hrs<BR>\n" );
document.write( "---<BR>\n" );
document.write( "6/(b-3) + 6/(b+3) = 8/3 hrs<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Multiply thru by 3(b-3)(b+3) to get:<BR>\n" );
document.write( "6*3(b+3) + 6*3(b-3) = 8(b^2-9)<BR>\n" );
document.write( "18b + 18b = 8b^2 - 72<BR>\n" );
document.write( "8b^2 - 36b - 72 = 0<BR>\n" );
document.write( "2b^2 - 9b - 18 = 0<BR>\n" );
document.write( "(b-6)(2b+3) = 0<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "b = 6 km (speed of the boat in still water)<BR>\n" );
document.write( "==============================================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );