document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1020892>Question 1020892</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat takes 3 hours to go 9 miles upstream. It can go 18 miles downstream in the same time. Find the rate of the current and the rate of the boat in still water.&#8203; (Hint: Because the current pushes the boat when it is going&#8203; downstream, the rate of the boat downstream is the sum of the rate of the boat and the rate of the current. The current slows down the boat when it is going&#8203; upstream, so the rate of the boat upstream is the difference of the rate of the boat and the rate of the&#8203; current.) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #636714 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><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=636714\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A boat takes 3 hours to go 9 miles upstream. It can go 18 miles downstream in the same time. Find the rate of the current and the rate of the boat in still water.&#8203; (Hint: Because the current pushes the boat when it is going&#8203; downstream, the rate of the boat downstream is the sum of the rate of the boat and the rate of the current. The current slows down the boat when it is going&#8203; upstream, so the rate of the boat upstream is the difference of the rate of the boat and the rate of the&#8203; current.)\r<BR>\n" );
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document.write( "let x=rate of boat in still water<BR>\n" );
document.write( "let c=rate of current<BR>\n" );
document.write( "(x+c)=rate of boat downsream<BR>\n" );
document.write( "(x-c)=rate of boat upsream<BR>\n" );
document.write( "travel time*rate=distance<BR>\n" );
document.write( "3(x-c)=9 (upstream)<BR>\n" );
document.write( "3(x+c)=18 (downstream)\r<BR>\n" );
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document.write( "3x-3c=9<BR>\n" );
document.write( "3x+3c=18<BR>\n" );
document.write( "add:<BR>\n" );
document.write( "6x=27<BR>\n" );
document.write( "x=4.5<BR>\n" );
document.write( "3c=18-3x=18-13.5=4.5<BR>\n" );
document.write( "c=1.5\r<BR>\n" );
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document.write( "rate of boat in still water=4.5 mph<BR>\n" );
document.write( "rate of current=1.5 mph\r<BR>\n" );
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document.write( " </SPAN>\n" );
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