document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=242521>Question 242521</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat goes 15 miles downstream. The return trip upstream takes 40 minutes longer. The boat can travel 12 miles per hour in still water. 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 #178082 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=178082\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A boat goes 15 miles downstream. The return trip upstream takes 40 minutes longer.<BR>\n" );
document.write( " The boat can travel 12 miles per hour in still water.<BR>\n" );
document.write( " What is the speed of the current? <BR>\n" );
document.write( ":<BR>\n" );
document.write( "let c = speed of the current<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(12-c) = speed upstream<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(12+c) = speed down stream<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Change 40 min to <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F3 ALIGN=MIDDLE  ALT=\"2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > hr<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Write a time equation; time = dist/speed<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Time upstream - time down stream = 40 min<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=15%2F%28%2812-c%29%29 ALIGN=MIDDLE  ALT=\"15%2F%28%2812-c%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > - <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=15%2F%28%2812%2Bc%29%29 ALIGN=MIDDLE  ALT=\"15%2F%28%2812%2Bc%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F3 ALIGN=MIDDLE  ALT=\"2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Multiply equation by 3(12+c)(12-c); results<BR>\n" );
document.write( ":<BR>\n" );
document.write( "3(12+c)*15 - 3(12-c)*15 = 2(12-c)(12+c)<BR>\n" );
document.write( ":<BR>\n" );
document.write( "45(12+c) - 45(12-c) = 2(144 - c^2)<BR>\n" );
document.write( ":<BR>\n" );
document.write( "540 + 45c - 540 + 45c = 288 - 2c^2<BR>\n" );
document.write( "Group like terms on the left<BR>\n" );
document.write( "2c^2 + 45c + 45c + 540 - 540 - 288 = 0<BR>\n" );
document.write( "which is<BR>\n" );
document.write( "2c^2 + 90c - 288 = 0<BR>\n" );
document.write( "Simplify, divide by 2<BR>\n" );
document.write( "c^2 + 45c - 144 = 0<BR>\n" );
document.write( "Factors to <BR>\n" );
document.write( "(c+48)(c-3) = 0<BR>\n" );
document.write( "positive solution<BR>\n" );
document.write( "c = 3 mph is the current<BR>\n" );
document.write( ":<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Check solution:<BR>\n" );
document.write( "15/9 - 15/15 = <BR>\n" );
document.write( "5/3 - 3/3 = 2/3<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );