document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=803654>Question 803654</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the speed of a river's current is 4mph. a boat travels 40 miles upstream at a constant rate of speed. if the speed has been 9mph faster, the trip would have taken 1 hour less time. what is the boat's speed 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 #484450 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=484450\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the speed of a river's current is 4mph. a boat travels 40 miles upstream at a constant rate of speed. if the speed has been 9mph faster, the trip would have taken 1 hour less time. what is the boat's speed in still water?\r<BR>\n" );
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document.write( "current speed = 4 mph<BR>\n" );
document.write( "boat speed in still water =x\r<BR>\n" );
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document.write( "upstream speed = x-4\r<BR>\n" );
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document.write( "t=d/r<BR>\n" );
document.write( "40/(x-4) hours\r<BR>\n" );
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document.write( "If spee}}}d was increased by 9 mph\r<BR>\n" );
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document.write( "speed = (x-4+9) = x+5 \r<BR>\n" );
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document.write( "t= 40/(x+5)\r<BR>\n" );
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document.write( "difference in time = 1 hour\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=40%2F%28x-4%29+-+40%2F%28x%2B5%29+=1 ALIGN=MIDDLE  ALT=\"40%2F%28x-4%29+-+40%2F%28x%2B5%29+=1\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "40(x+5)-40(x-4) =(x-4)(x+5)*1\r<BR>\n" );
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document.write( "40x+200-40x+160=x^2+x-20\r<BR>\n" );
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document.write( "x^2+x-380=0\r<BR>\n" );
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document.write( "x^2+20x-19x-380=0\r<BR>\n" );
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document.write( "x(x+20)-19(x+20)=0\r<BR>\n" );
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document.write( "(x+20)(x-19)=0\r<BR>\n" );
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document.write( "x=-20 OR 19\r<BR>\n" );
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document.write( "ignore negative\r<BR>\n" );
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document.write( "speed in still water = 19mph </SPAN>\n" );
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