document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=163285>Question 163285</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How many gallons of a 30% acid solution must be mixed with 30 gallons of a 17% solution to obtain a solution that is 20% acid.\r<BR>\n" );
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document.write( "I've tried this problem a couple times, but cant get the right answer. The answer was given to me by my teacher, but I need to show how to do the problem, which I can't. The answer to the problem is 9, i would appreciate it if you explained how to do the problem thoroughly. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #120307 by </B><A HREF=/tutors/aboutme.mpl?userid=Anthea+Lawn><B>Anthea Lawn(22)</B></A><img src=\"/images/stars/stars-07.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Anthea+Lawn><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=120307\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> First of all, consider : How much pure acid is in 30 gallons of 17% acid ?<BR>\n" );
document.write( "The answer is 17% of it : 17% X 30 = 0.17 X 30 = 5.1 gallons of pure acid\r<BR>\n" );
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document.write( "Now, start thinking about the 30% acid.<BR>\n" );
document.write( "If you have N gallons of the stuff, how much of THAT is pure acid ?<BR>\n" );
document.write( "The answer is 30% of N, or expressed algebraically, 0.3N.\r<BR>\n" );
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document.write( "If you mix the 30 gallons of 17% acid with N gallons of 30% acid, how many gallons of acid in total will there be ?<BR>\n" );
document.write( "answer : 30 + N gallons in total\r<BR>\n" );
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document.write( "And of that, the amount which is pure acid is 5.1 (from above) + 0.3N.\r<BR>\n" );
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document.write( "The concentration of the mix is given by the number of gallons of pure acid divided by gallons of total acid,<BR>\n" );
document.write( "which is :<BR>\n" );
document.write( "(5.1 + 0.3N)/(30 + N)\r<BR>\n" );
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document.write( "Now we know that want the resulting concentration to by 20%, or, to put it another way, one fifth\r<BR>\n" );
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document.write( "(5.1 + 0.3N)/(30 + N)  =   1/5\r<BR>\n" );
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document.write( "5(5.1 + 0.3N) = 30 + N\r<BR>\n" );
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document.write( "25.5 + 1.5N = 30 + N\r<BR>\n" );
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document.write( "4.5 = 0.5N\r<BR>\n" );
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document.write( "N = 9  (which was the answer you had)\r<BR>\n" );
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document.write( "Hope that helps !!\r<BR>\n" );
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document.write( " </SPAN>\n" );
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