document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1183385>Question 1183385</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hello\r<BR>\n" );
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document.write( "A pipe can empty a tank in 40 minutes.<BR>\n" );
document.write( "A second pipe with diameter twice as much as<BR>\n" );
document.write( " that of the first is also attached with the tank to empty it.\r<BR>\n" );
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document.write( "The two pipes together can empty the tank in 8<BR>\n" );
document.write( "minutes.\r<BR>\n" );
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document.write( "I don't understand how they got 8?\r<BR>\n" );
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document.write( "How would I go about solving this?\r<BR>\n" );
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document.write( "Thanks in advance,\r<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 #813690 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=813690\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "The rate at which water flows through the pipes is proportional to the cross sectional area of the pipes.  Since the diameter of the second pipe is 2 times the diameter of the first, water flows through the second pipe at a rate 2^2=4 times as fast as through the first pipe.<br><BR>\n" );
document.write( "So having both pipes working is like having 1+4=5 of the first pipes.  Then, since the first pipe can empty the tank in 40 minutes, the two pipes together can empty it in 40/5 = 8 minutes.<br><BR>\n" );
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document.write( "Note that a couple of tutors who responded to this post failed to understand what the reader was asking for.<br><BR>\n" );
document.write( "He KNOWS the answer is 8 minutes; what he is clearly asking for is help to understand HOW to get that answer.<br><BR>\n" );
document.write( "My response above and the one from tutor @Math_helper both do that, in different ways....<br><BR>\n" );
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