document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=910315>Question 910315</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat can travel 60 km/h in calm water.  The boat travels 200 km against the current and then returns to the location where it started.  If the trip takes 10 total hours, what is the speed of the current?\r<BR>\n" );
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document.write( "I started with t = dr to r = t/d<BR>\n" );
document.write( "(1/60) x 10 = 10/600<BR>\n" );
document.write( "10/200 = 10/600<BR>\n" );
document.write( "cross multiply = 6000/2000=3<BR>\n" );
document.write( "I don't know if 3 would be the answer or if I have to do more, or if its the answer I don't know if its the right answer.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #552428 by </B><A HREF=/tutors/aboutme.mpl?userid=richwmiller><B>richwmiller(17219)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richwmiller><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=richwmiller><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=552428\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> r*t=d<BR>\n" );
document.write( "200/(60-c)+200/(60+c)=10/1<BR>\n" );
document.write( "Multiply thru by 1*(60-c)(60+c)<BR>\n" );
document.write( "200*1*(60+c)+200*1(60-c)=10(c^2-3600)<BR>\n" );
document.write( "200*60+200*c+200*60-200*c=10*c^2-10*3600<BR>\n" );
document.write( "12000+200*c+12000-200*c=10*c^2-36000<BR>\n" );
document.write( "0=10*c^2-36000+(24000)+(0)*c<BR>\n" );
document.write( "10*c^2+-12000=0<BR>\n" );
document.write( "10*c^2+-12000=0<BR>\n" );
document.write( "c=34.641\r<BR>\n" );
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document.write( "<TABLE  BORDER=1>\n" );
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document.write( " <TR><TD  ALIGN=MIDDLE>Solved by <A  rel=nofollow HREF=http://wiki.algebra.com/index.php/Tutoring_-_pluggable_solvers>pluggable</A> solver: <A  rel=nofollow HREF=quadratic.solver>SOLVE quadratic equation with variable</A></TD></TR>\n" );
document.write( "<TR><TD  ALIGN=LEFT>Quadratic equation <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ac%5E2%2Bbc%2Bc=0 ALIGN=MIDDLE  ALT=\"ac%5E2%2Bbc%2Bc=0\"   DISABLED_style= \"max-width:90%; height:auto;\" > (in our case <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10c%5E2%2B0c%2B-12000+=+0 ALIGN=MIDDLE  ALT=\"10c%5E2%2B0c%2B-12000+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" >) has the following solutons:<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=c%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca ALIGN=MIDDLE  ALT=\"c%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <BR>\n" );
document.write( "  For these solutions to exist, the <U>discriminant</U> <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac ALIGN=MIDDLE  ALT=\"b%5E2-4ac\"   DISABLED_style= \"max-width:90%; height:auto;\" > should not be a negative number.<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  First, we need to compute the discriminant <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac ALIGN=MIDDLE  ALT=\"b%5E2-4ac\"   DISABLED_style= \"max-width:90%; height:auto;\" >: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac=%280%29%5E2-4%2A10%2A-12000=480000 ALIGN=MIDDLE  ALT=\"b%5E2-4ac=%280%29%5E2-4%2A10%2A-12000=480000\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  Discriminant d=480000 is greater than zero. That means that there are two solutions: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+x%5B12%5D+=+%28-0%2B-sqrt%28+480000+%29%29%2F2%5Ca ALIGN=MIDDLE  ALT=\"+x%5B12%5D+=+%28-0%2B-sqrt%28+480000+%29%29%2F2%5Ca\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "  <BR>\n" );
document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=c%5B1%5D+=+%28-%280%29%2Bsqrt%28+480000+%29%29%2F2%5C10+=+34.6410161513775 ALIGN=MIDDLE  ALT=\"c%5B1%5D+=+%28-%280%29%2Bsqrt%28+480000+%29%29%2F2%5C10+=+34.6410161513775\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=c%5B2%5D+=+%28-%280%29-sqrt%28+480000+%29%29%2F2%5C10+=+-34.6410161513775 ALIGN=MIDDLE  ALT=\"c%5B2%5D+=+%28-%280%29-sqrt%28+480000+%29%29%2F2%5C10+=+-34.6410161513775\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "    <BR>\n" );
document.write( "    Quadratic expression <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10c%5E2%2B0c%2B-12000 ALIGN=MIDDLE  ALT=\"10c%5E2%2B0c%2B-12000\"   DISABLED_style= \"max-width:90%; height:auto;\" > can be factored:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10c%5E2%2B0c%2B-12000+=+10%28c-34.6410161513775%29%2A%28c--34.6410161513775%29 ALIGN=MIDDLE  ALT=\"10c%5E2%2B0c%2B-12000+=+10%28c-34.6410161513775%29%2A%28c--34.6410161513775%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  Again, the answer is: 34.6410161513775, -34.6410161513775.\n" );
document.write( "Here's your graph:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+10%2Ax%5E2%2B0%2Ax%2B-12000+%29 ALIGN=MIDDLE  ALT=\"graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+10%2Ax%5E2%2B0%2Ax%2B-12000+%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ></TD></TR>\n" );
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document.write( " </SPAN>\n" );
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