document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=876967>Question 876967</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 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 #529065 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=529065\">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( "Going upstream:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5+=+%28+s+-+4+%29%2At%5B1%5D+ ALIGN=MIDDLE  ALT=\"+5+=+%28+s+-+4+%29%2At%5B1%5D+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Going downstream:<BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+13+=+%28+s+%2B+4+%29%2At%5B2%5D+ ALIGN=MIDDLE  ALT=\"+13+=+%28+s+%2B+4+%29%2At%5B2%5D+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t%5B1%5D+%2B+t%5B2%5D+=+2+ ALIGN=MIDDLE  ALT=\"+t%5B1%5D+%2B+t%5B2%5D+=+2+\"   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%5B1%5D+=+5+%2F+%28+s+-+4+%29+ ALIGN=MIDDLE  ALT=\"+t%5B1%5D+=+5+%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=+t%5B2%5D+=+13+%2F+%28+s+%2B+4+%29+ ALIGN=MIDDLE  ALT=\"+t%5B2%5D+=+13+%2F+%28+s+%2B+4+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "-------------------------<BR>\n" );
document.write( "By substitution:<BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5+%2F+%28+s+-+4+%29+%2B+13+%2F+%28+s+%2B+4+%29+=+2+ ALIGN=MIDDLE  ALT=\"+5+%2F+%28+s+-+4+%29+%2B+13+%2F+%28+s+%2B+4+%29+=+2+\"   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=+%28+s+-+4+%29%2A%28+s+%2B+4+%29+ ALIGN=MIDDLE  ALT=\"+%28+s+-+4+%29%2A%28+s+%2B+4+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5%2A%28+s+%2B+4+%29+%2B+13%2A%28+s+-+4+%29+=+2%2A%28+s%5E2+-+16+%29+ ALIGN=MIDDLE  ALT=\"+5%2A%28+s+%2B+4+%29+%2B+13%2A%28+s+-+4+%29+=+2%2A%28+s%5E2+-+16+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5s+%2B+20+%2B+13s+-+52+=+2s%5E2+-+32+ ALIGN=MIDDLE  ALT=\"+5s+%2B+20+%2B+13s+-+52+=+2s%5E2+-+32+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+2s%5E2+-+18s+=+0+ ALIGN=MIDDLE  ALT=\"+2s%5E2+-+18s+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s%5E2+-+9s+=+0+ ALIGN=MIDDLE  ALT=\"+s%5E2+-+9s+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s%2A%28+s+-+9+%29+=+0+ ALIGN=MIDDLE  ALT=\"+s%2A%28+s+-+9+%29+=+0+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+s+=+9+ ALIGN=MIDDLE  ALT=\"+s+=+9+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The speed of the boat in still water in 9 mi/hr<BR>\n" );
document.write( "--------------<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5+=+%28+s+-+4+%29%2At%5B1%5D+ ALIGN=MIDDLE  ALT=\"+5+=+%28+s+-+4+%29%2At%5B1%5D+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+5+=+%28+9+-+4+%29%2At%5B1%5D+ ALIGN=MIDDLE  ALT=\"+5+=+%28+9+-+4+%29%2At%5B1%5D+\"   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%5B1%5D+=+1+ ALIGN=MIDDLE  ALT=\"+t%5B1%5D+=+1+\"   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=+13+=+%28+s+%2B+4+%29%2At%5B2%5D+ ALIGN=MIDDLE  ALT=\"+13+=+%28+s+%2B+4+%29%2At%5B2%5D+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+13+=+%28+9+%2B+4+%29%2At%5B2%5D+ ALIGN=MIDDLE  ALT=\"+13+=+%28+9+%2B+4+%29%2At%5B2%5D+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t%5B2%5D+=+1+ ALIGN=MIDDLE  ALT=\"+t%5B2%5D+=+1+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+t%5B1%5D+%2B+t%5B2%5D+=+2+ ALIGN=MIDDLE  ALT=\"+t%5B1%5D+%2B+t%5B2%5D+=+2+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "(3) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+1+%2B+1+=+2+ ALIGN=MIDDLE  ALT=\"+1+%2B+1+=+2+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "OK<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );