document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=416168>Question 416168</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a river boat tour begins by going 60 miles upstream against a 5 mph current.  Then the boat turns around and returns with the current.  What still-water speed should the captain use to complete the tour in 5 hours? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #291629 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=291629\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> let speed in still water =x mph			<BR>\n" );
document.write( "current speed 	4 mph			<BR>\n" );
document.write( "					<BR>\n" );
document.write( "upstream speed = x-4					<BR>\n" );
document.write( "downstream speed = x+4					<BR>\n" );
document.write( "					<BR>\n" );
document.write( "Distance= 60 miles			<BR>\n" );
document.write( "					<BR>\n" );
document.write( "Time upstream + time downstream = 5 hours	<BR>\n" );
document.write( "t=d/r					<BR>\n" );
document.write( "60/(x+4)+60(x-4)=5				<BR>\n" );
document.write( "LCD =(x	-4)(x+4)								<BR>\n" );
document.write( "60*(x-4)+60(x+4)=5				<BR>\n" );
document.write( "60x-240	+60x+240=5(X^2-16)<BR>\n" );
document.write( "120x=5X^2-80								<BR>\n" );
document.write( "5X^2-120x-80<BR>\n" );
document.write( "a= 5, b= -120, c=-80<BR>\n" );
document.write( "b^2-4ac= 12800<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x1=%28120%2Bsqrt%2812800%29%29%2F%2810%29 ALIGN=MIDDLE  ALT=\"x1=%28120%2Bsqrt%2812800%29%29%2F%2810%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "x1=23.3 mph\r<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x2=%28120-sqrt%2812800%29%29%2F%2810%29 ALIGN=MIDDLE  ALT=\"x2=%28120-sqrt%2812800%29%29%2F%2810%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "=0.69 -- not practical<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );