document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1071860>Question 1071860</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The speed of a river current is 4 mph. If a boat travels 20 miles downstream in the same time that it takes to travel 10 miles&#8203; upstream, find the speed of the boat in still water.<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #686780 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=686780\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> current is 4 mph<BR>\n" );
document.write( "speed of boat =x<BR>\n" );
document.write( "downstream, speed is 4+x and time is 20/x+4, because time is distance over speed.<BR>\n" );
document.write( "upstream, speed is 4-x and time is 10/x-4<BR>\n" );
document.write( "The two times are equal<BR>\n" );
document.write( "so 20/x+4=10/x-4<BR>\n" );
document.write( "20x-80=10x+40<BR>\n" );
document.write( "10x=120<BR>\n" );
document.write( "x=12 mph<BR>\n" );
document.write( "16 mph downstream and takes 1h15m to go 20 miles (1.25 hr)<BR>\n" );
document.write( "8 mph upstream and takes 1h15m to go 10 miles. </SPAN>\n" );
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