document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=435711>Question 435711</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Forty pounds of an alloy of copper and tin contain 8 pounds of copper. How many pounds of tin must be added to make a new alloy that is 10% copper?\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 #301526 by </B><A HREF=/tutors/aboutme.mpl?userid=rwm><B>rwm(914)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rwm><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=301526\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Right now the alloy has 8/40=1/5 copper <BR>\n" );
document.write( "so we want half of that 1/10 to be copper.\r<BR>\n" );
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document.write( "The temptation is to double the tin amount to 64 instead of the present 32.<BR>\n" );
document.write( "but <BR>\n" );
document.write( "We double the total amount not just the tin.<BR>\n" );
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document.write( "1/10=8/80\r<BR>\n" );
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document.write( "80-40=40<BR>\n" );
document.write( "so we add 40 lbs of tin to have a total of 80 lbs.<BR>\n" );
document.write( "we could write it <BR>\n" );
document.write( ".9a+.1a=40+x<BR>\n" );
document.write( ".1a=8<BR>\n" );
document.write( "where a=80 and x=40\r<BR>\n" );
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