document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=152435>Question 152435</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Your boat will go 15 miles per hour in still water.  If you can go 12 miles downstream in the same amount of time it takes to go 9 miles upstream, then what is the speed of the current? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #112059 by </B><A HREF=/tutors/aboutme.mpl?userid=ptaylor><B>ptaylor(2198)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ptaylor><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=ptaylor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=112059\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Distance(d) equals rate(r) times Time(t) or d=rt; r=d/t and t=d/r\r<BR>\n" );
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document.write( "Let r=rate(speed) of the current<BR>\n" );
document.write( "(We know that speed upstream=15-r and speed downstream=15+r)\r<BR>\n" );
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document.write( "Time to go upstream=9/(15-r)<BR>\n" );
document.write( "Time to go downstream=12/(15+r)\r<BR>\n" );
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document.write( "Now we are told that the above two times are equal, so our equation to solve is:\r<BR>\n" );
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document.write( "9/(15-r)=12/(15+r)  multiply each side by (15-r)(15+r) or cross multiply\r<BR>\n" );
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document.write( "9(15+r)=12(15-r)  get rid of paren<BR>\n" );
document.write( "135+9r=180-12r  subtract 135 from and add 12r to each side\r<BR>\n" );
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document.write( "135-135+9r+12r=180-135-12r+12r  collect like terms\r<BR>\n" );
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document.write( "21r=45  divide each side by 21\r<BR>\n" );
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document.write( "r=2 1/7 mph---------------------speed of current\r<BR>\n" );
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document.write( "CK<BR>\n" );
document.write( "9/(15-2 1/7)=12/(15+2 1/7) or<BR>\n" );
document.write( "9/(12 6/7)=12/(17 1/7) and this equals<BR>\n" );
document.write( "9/(90/7)=12/(120/7) or<BR>\n" );
document.write( "63/90=84/120 and<BR>\n" );
document.write( "7/10=7/10\r<BR>\n" );
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document.write( "Hope this helps----ptaylor </SPAN>\n" );
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