document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=132577>Question 132577</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Aubry's boat goes 20 mph in still water.  It travels 75 miles upstream and back in a total time of 8 hours.  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 #96900 by </B><A HREF=/tutors/aboutme.mpl?userid=mathispowerful><B>mathispowerful(115)</B></A><img src=\"/images/stars/stars-09.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mathispowerful><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=96900\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Since total time is 8 hours:\r<BR>\n" );
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document.write( "If we let x be the current speed, the upstream speed is\r<BR>\n" );
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document.write( "20-x, downstream speed is 20+x\r<BR>\n" );
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document.write( "So  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=75%2F%2820-x%29%2B75%2F%2820%2Bx%29=8 ALIGN=MIDDLE  ALT=\"75%2F%2820-x%29%2B75%2F%2820%2Bx%29=8\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Multiply (20-x)(20+x) on both sides:\r<BR>\n" );
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document.write( "75(20+x)+75(20-x)=8(20-x)(20+x)\r<BR>\n" );
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document.write( "simplify it we get:\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3000=8%28400-x%5E2%29 ALIGN=MIDDLE  ALT=\"3000=8%28400-x%5E2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3000+=+3200-8x%5E2 ALIGN=MIDDLE  ALT=\"3000+=+3200-8x%5E2\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "That is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8x%5E2=3200-3000 ALIGN=MIDDLE  ALT=\"8x%5E2=3200-3000\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8x%5E2=200 ALIGN=MIDDLE  ALT=\"8x%5E2=200\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5E2=25 ALIGN=MIDDLE  ALT=\"x%5E2=25\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "x=5\r<BR>\n" );
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document.write( "So the answer is 5 miles/hr. </SPAN>\n" );
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