document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1201539>Question 1201539</A>: <I><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "A boat takes 12 hours to cover (D+30) km in upstream and it takes 8 hours to cover D km in downstream. If speed of stream is 4<BR>\n" );
document.write( "km/hr, then find the time (in hours) taken by boat to cover (D-64) km in upstream. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #835955 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=835955\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> upstreatm, the boat is traveling against the current.<BR>\n" );
document.write( "downstream, the boat is traveling with the current.\r<BR>\n" );
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document.write( "your equations are:\r<BR>\n" );
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document.write( "12 * (R - 4) = D + 30<BR>\n" );
document.write( "8 * (R + 4) = D<BR>\n" );
document.write( "simplify to get:<BR>\n" );
document.write( "12 * R - 48 = D + 30<BR>\n" );
document.write( "8 * R + 32 = D<BR>\n" );
document.write( "subtract 30 from both sides of the first equqtion and leave the second equation as is to get:<BR>\n" );
document.write( "12 * R - 78 = D<BR>\n" );
document.write( "8 * R + 32 = D<BR>\n" );
document.write( "since both equation are equal to D, you can set them equal to each other to get:<BR>\n" );
document.write( "12 * R - 78 = 8 * R + 32<BR>\n" );
document.write( "add 78 to both sides of the equation and subtract 8 * R from both sides of the equastion to get:<BR>\n" );
document.write( "4 * R = 110<BR>\n" );
document.write( "solve for R to get:<BR>\n" );
document.write( "R = 110 / 4 = 27.5<BR>\n" );
document.write( "replace R with that in your two original equations to get:<BR>\n" );
document.write( "12 * R - 78 = D becomes 12 * 27.5 - 78 = 252<BR>\n" );
document.write( "8 * R + 32 = D becomes 8 * 27.5 + 32 = 252<BR>\n" );
document.write( "it appears that R = 27.5 is good and that D = 252 is also good.<BR>\n" );
document.write( "you are asked to find how long it takes the boat to travel D - 64 kilometers upstream.<BR>\n" );
document.write( "upstream, the boat is traveling against the current, therefore (R - 4) * T = D - 64<BR>\n" );
document.write( "since R is 27.5 and D is 252, the equation becomes 23.5 * T = 188.<BR>\n" );
document.write( "solve for T to get:<BR>\n" );
document.write( "T = 188 / 23.5 = 8<BR>\n" );
document.write( "it takes the boat 8 hours to travel 188 kilometers upstream.<BR>\n" );
document.write( "that's your solution.<BR>\n" );
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