document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1207335>Question 1207335</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi<BR>\n" );
document.write( "Mark bought a number of pens at an average cost of $2.50 He bought another pen for $8.50 and the average cost of the pens became $4.50. How many pens did he buy altogether. <BR>\n" );
document.write( "Thanks </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #845158 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=845158\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "Here is a very unorthodox method for solving a problem like this....  A bit difficult to learn; but if you can learn it, it is much faster than the formal algebraic solution method.  Of course, if a formal algebraic solution is needed, this won't help you.<br><BR>\n" );
document.write( "We can treat this as a \"mixture\" problem -- we are \"mixing\" pens that cost $2.50 each with pens that cost $8.50 each to get a \"mixture\" of pens that cost an average of $4.50 each.<br><BR>\n" );
document.write( "For an unorthodox method for solving that problem, look at the three numbers 2.50, 4.50, and 8.50 (on a number line, if it helps) and observe/calculate that 4.50 is 1/3 of the way from 2.50 to 8.50 (from 2.50 to 8.50 is a difference of 6; from 2.50 to 4.50 is a difference of 2; 2/6 = 1/3).<br><BR>\n" );
document.write( "That means 1/3 of the pens were the more expensive ones.  Then, since there was one $8.50 pen, the total number of pens was 3.<br><BR>\n" );
document.write( "ANSWER: 3 pens (1 at $8.50 and 2 at $2.50 each)<br><BR>\n" );
document.write( "CHECK:<BR>\n" );
document.write( "$8.50 + 2($2.50) = $13.50<BR>\n" );
document.write( "3($4.50) = $13.50<br><BR>\n" );
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