document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=172429>Question 172429</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns in a total of 8 hours. What is the speed of the boat 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 #127448 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=127448\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns<BR>\n" );
document.write( " in a total of 8 hours. What is the speed of the boat in still water?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Let s = boat speed in still water<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(s-5) = speed upstream<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(s+5) = speed down stream<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Write a time equation: Time= <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=dist%2Fspeed ALIGN=MIDDLE  ALT=\"dist%2Fspeed\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( ":<BR>\n" );
document.write( "Time upstream + time downstream = 8 hours<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=75%2F%28%28s-5%29%29 ALIGN=MIDDLE  ALT=\"75%2F%28%28s-5%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=75%2F%28%28s%2B5%29%29 ALIGN=MIDDLE  ALT=\"75%2F%28%28s%2B5%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 8<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Multiply equation by (s-5)(s+5)<BR>\n" );
document.write( "(s-5)(s+5)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=75%2F%28%28s-5%29%29 ALIGN=MIDDLE  ALT=\"75%2F%28%28s-5%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > + (s-5)(s+5)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=75%2F%28%28s%2B5%29%29 ALIGN=MIDDLE  ALT=\"75%2F%28%28s%2B5%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 8(s-5)(s+5)<BR>\n" );
document.write( "results<BR>\n" );
document.write( "75(s+5) + 75(s-5) = 8(s^2 - 25)<BR>\n" );
document.write( ":<BR>\n" );
document.write( "75s + 375 + 75s - 375 = 8s^2 - 200<BR>\n" );
document.write( ":<BR>\n" );
document.write( "150s = 8s^2 - 200<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Arrange as a quadratic equation <BR>\n" );
document.write( "8s^2 - 150s - 200 = 0<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Simplify divide equation by 2:<BR>\n" );
document.write( "4s^2 - 75s - 100 = 0<BR>\n" );
document.write( "Factors to:<BR>\n" );
document.write( "(4s + 5)(s - 20) = 0<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "s = +20 speed of boat in still water<BR>\n" );
document.write( ":<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Check the solution by finding the times of up and down streams<BR>\n" );
document.write( "75/15 = 5 hrs<BR>\n" );
document.write( "75/25 = 3 hrs<BR>\n" );
document.write( "-------------<BR>\n" );
document.write( "total = 8 hrs </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );