document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=655526>Question 655526</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I really need help.\r<BR>\n" );
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document.write( "A tugboat goes 140miles upstream in 10 hours. The return trip downstream takes 5 hours. Find the speed.<BR>\n" );
document.write( "the speed pf the tugboat is ___mph, and the speed of the current is ___mph. \r<BR>\n" );
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document.write( "this is substitution to solve linear equations. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #409166 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=409166\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let c = speed of the current and s = speed of the boat\r<BR>\n" );
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document.write( "Going upstream, the boat is fighting against the current. So its speed goes from 's' mph to s-c mph\r<BR>\n" );
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document.write( "Therefore, the equation going 140 miles upstream in 10 hrs is\r<BR>\n" );
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document.write( "d = rt\r<BR>\n" );
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document.write( "140 = (s-c)*10\r<BR>\n" );
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document.write( "140/10 = s-c\r<BR>\n" );
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document.write( "14 = s-c\r<BR>\n" );
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document.write( "Solve for s to get \r<BR>\n" );
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document.write( "14 + c = s\r<BR>\n" );
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document.write( "s = 14 + c \r<BR>\n" );
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document.write( "Returning downstream, you pick up speed. So you go from 's' mph to s+c mph\r<BR>\n" );
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document.write( "So going 140 miles downstream in 5 hours means\r<BR>\n" );
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document.write( "d = rt\r<BR>\n" );
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document.write( "140 = (s+c)*5\r<BR>\n" );
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document.write( "140/5 = s+c\r<BR>\n" );
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document.write( "28 = s+c\r<BR>\n" );
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document.write( "s+c = 28\r<BR>\n" );
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document.write( "Now plug in s = 14 + c and solve for c\r<BR>\n" );
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document.write( "s+c = 28\r<BR>\n" );
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document.write( "14+c+c = 28\r<BR>\n" );
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document.write( "14+2c = 28\r<BR>\n" );
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document.write( "2c = 28-14\r<BR>\n" );
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document.write( "2c = 14\r<BR>\n" );
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document.write( "c = 14/2\r<BR>\n" );
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document.write( "c = 7\r<BR>\n" );
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document.write( "So the speed of the current is 7 mph\r<BR>\n" );
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document.write( "s = 14+c\r<BR>\n" );
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document.write( "s = 14+7\r<BR>\n" );
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document.write( "s = 21\r<BR>\n" );
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document.write( "and the speed of the boat is 21 mph\r<BR>\n" );
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document.write( " </SPAN>\n" );
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