document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=359419>Question 359419</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The mean of a set of numbers is 120. If one number is increased by 300, the mean equals 135. How many numbers are in the set? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #256469 by </B><A HREF=/tutors/aboutme.mpl?userid=jrfrunner><B>jrfrunner(365)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jrfrunner><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=jrfrunner><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=256469\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> average = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%28x%29%2Fn ALIGN=MIDDLE  ALT=\"sum%28x%29%2Fn\"   DISABLED_style= \"max-width:90%; height:auto;\" >  therefore <BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2Aaverage=sum%28x%29 ALIGN=MIDDLE  ALT=\"n%2Aaverage=sum%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "===<BR>\n" );
document.write( "given<BR>\n" );
document.write( "average=120 then we have the relationship  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2A120=sum%28x%29 ALIGN=MIDDLE  ALT=\"n%2A120=sum%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "--<BR>\n" );
document.write( "also if one number is increased by 300 (this means that <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%28x%29 ALIGN=MIDDLE  ALT=\"sum%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > increases by 300) and the average =135<BR>\n" );
document.write( "thus   <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2A135=sum%28x%29%2B300 ALIGN=MIDDLE  ALT=\"n%2A135=sum%28x%29%2B300\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "--<BR>\n" );
document.write( "So you have two equations and two unknowns, solve for n\r<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2A120=sum%28x%29 ALIGN=MIDDLE  ALT=\"n%2A120=sum%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2A135=sum%28x%29%2B300 ALIGN=MIDDLE  ALT=\"n%2A135=sum%28x%29%2B300\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "--<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%2A135-n%2A120=sum%28x%29%2B300-sum%28x%29 ALIGN=MIDDLE  ALT=\"n%2A135-n%2A120=sum%28x%29%2B300-sum%28x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >  subtract the second equation from the first<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=15n=300 ALIGN=MIDDLE  ALT=\"15n=300\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "n=300/15=20\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "  <BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );