document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=388616>Question 388616</A>: <I><SPAN STYLE=\"word-break: break-all;\"> speed of a boat in still wateris 9km/hr.It goes 12km down stream and comes back to the starting point in 3hrs.What is the speed of water in the stream? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #274977 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=274977\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> speed of a boat in still wateris 9km/hr.It goes 12km down stream and comes back to the starting point in 3hrs.What is the speed of water in the stream?<BR>\n" );
document.write( "...<BR>\n" );
document.write( "boat speed = 9 km/h<BR>\n" );
document.write( "speed of current = x km/h<BR>\n" );
document.write( "...<BR>\n" );
document.write( "upstream speed = 9-x<BR>\n" );
document.write( "downstream speed = 9+x<BR>\n" );
document.write( "..<BR>\n" );
document.write( "time downstream + time upstream = 3 hours<BR>\n" );
document.write( "..<BR>\n" );
document.write( "t=d/r<BR>\n" );
document.write( "..<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%2F%289-x%29%2B12%2F%289%2Bx%29=3 ALIGN=MIDDLE  ALT=\"12%2F%289-x%29%2B12%2F%289%2Bx%29=3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "...<BR>\n" );
document.write( "LCD = (9+x)(9-x)<BR>\n" );
document.write( "multiply by LCD<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2812%289%2Bx%29-12%289-x%29%29%2F%28%289%2Bx%29%289-x%29%29 ALIGN=MIDDLE  ALT=\"%2812%289%2Bx%29-12%289-x%29%29%2F%28%289%2Bx%29%289-x%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >=3<BR>\n" );
document.write( "(108+12x-108+12x)=3(9+x)(9-x)<BR>\n" );
document.write( "24x=3(81-x^2)<BR>\n" );
document.write( "/3<BR>\n" );
document.write( "8x=81-x^2<BR>\n" );
document.write( "x^2+8x-81=0<BR>\n" );
document.write( "find roots x1,x2 by using quadratic formula<BR>\n" );
document.write( "discriminant = b^2-4ac = 388<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x1=%28-8%2Bsqrt%28388%29%29%2F%282%29 ALIGN=MIDDLE  ALT=\"x1=%28-8%2Bsqrt%28388%29%29%2F%282%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28highlight%28x1=5.85%29%29 ALIGN=MIDDLE  ALT=\"%28highlight%28x1=5.85%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > km/h speed of current<BR>\n" );
document.write( "..<BR>\n" );
document.write( "x2 will be negative so ignore<BR>\n" );
document.write( "...<BR>\n" );
document.write( "m.ananth@hotmail.ca </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );