document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1200052>Question 1200052</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What amount of pure acid must be added to 500 mL of a 25% acid solution to produce a 50% acid solution?<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #834078 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=834078\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "The response from the other tutor shows a standard formal algebraic solution -- which you should understand, if you are a student learning how to solve problems using algebra.<br><BR>\n" );
document.write( "If the speed of obtaining the answer is important and any method can be used (as in a timed math competition), here is an informal solution method that is much faster and easier than the formal algebraic method.<br><BR>\n" );
document.write( "The 50% target concentration is 1/3 of the way from the 25% concentration of the original acid solution to the 100% concentration of the acid that is added. (25 to 50 is a difference of 25; 25 to 100 is a difference of 75; 25/75 = 1/3.)<br><BR>\n" );
document.write( "That means 1/3 of the mixture should be what is being added.<br><BR>\n" );
document.write( "So 2/3 of the final mixture is the original 25% acid solution; and that means the amount of 100% acid being added is half the amount of the original 25% acid solution.<br><BR>\n" );
document.write( "ANSWER: 1/2 of 500 mL = 250 mL<br><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );