document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=503698>Question 503698</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A student weighs 885 pennies and finds them to have a mass of 2500.4g. If the pre-1982 pennies weigh an average 3.09g and the post-1982 pennies weigh 2.51 g. How many of pennies are pre-1982 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #339370 by </B><A HREF=/tutors/aboutme.mpl?userid=oberobic><B>oberobic(2304)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=oberobic><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=339370\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> X = count of old pennies<BR>\n" );
document.write( "3.09*X = weight of old pennies<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Y = count of new pennies<BR>\n" );
document.write( "2.51*Y = weight of new pennies<BR>\n" );
document.write( ".<BR>\n" );
document.write( "X+Y = 885 pennies<BR>\n" );
document.write( "Y = 885-X<BR>\n" );
document.write( ".<BR>\n" );
document.write( "3.09*X + 2.51*Y = 2500.4<BR>\n" );
document.write( ".<BR>\n" );
document.write( "multiply by 100 to remove decimals<BR>\n" );
document.write( ".<BR>\n" );
document.write( "309X + 251Y = 250040<BR>\n" );
document.write( ".<BR>\n" );
document.write( "substitute for Y = 885-X<BR>\n" );
document.write( ".<BR>\n" );
document.write( "309X + 251(885-X) = 250040<BR>\n" );
document.write( ".<BR>\n" );
document.write( "309X + 222135 -251X = 250040<BR>\n" );
document.write( "309X -251X = 250040 - 222135<BR>\n" );
document.write( "58X = 27905<BR>\n" );
document.write( ".<BR>\n" );
document.write( "X = 481.12<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Recall, we do not have counts but instead have average weights.<BR>\n" );
document.write( "So having a result that is not an integer is to be expected.<BR>\n" );
document.write( "We can assume X = 481.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "That means<BR>\n" );
document.write( "Y = 885 - 481<BR>\n" );
document.write( "Y = 404<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Always check your work.<BR>\n" );
document.write( "3.09 * 481 = 1486.29<BR>\n" );
document.write( "2.51 * 404 =  1014.04<BR>\n" );
document.write( "1486.29+1014.04 = 2500.33<BR>\n" );
document.write( "Compared to 2500.4, it's close.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Answer:  There were 481 older pennies and 404 newer pennies. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );