document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1043690>Question 1043690</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The number of emails you sent can be modelled by the equation\r<BR>\n" );
document.write( "\n" );
document.write( "u = 20×(1.8)^e,\r<BR>\n" );
document.write( "\n" );
document.write( "where u is the total number of emails sent, and e is the number of<BR>\n" );
document.write( "months since you started sending emails, where 0&#8804; e &#8804; 8.\r<BR>\n" );
document.write( "\n" );
document.write( "1 -  find the month in which the exponential model predicts that the total<BR>\n" );
document.write( "number of emails sent will first reach 500?\r<BR>\n" );
document.write( "\n" );
document.write( "2 -  Write down the value of the scale factor for the exponential<BR>\n" );
document.write( "model. Use this to find the percentage increase in the total<BR>\n" );
document.write( "number of emails sent?<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 #658851 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=658851\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The number of emails you sent can be modelled by the equation\r<BR>\n" );
document.write( "\n" );
document.write( "u = 20×(1.8)^e,\r<BR>\n" );
document.write( "\n" );
document.write( "where u is the total number of emails sent, and e is the number of<BR>\n" );
document.write( "months since you started sending emails, where 0&#8804; e &#8804; 8.\r<BR>\n" );
document.write( "\n" );
document.write( "1 -  find the month in which the exponential model predicts that the total<BR>\n" );
document.write( "number of emails sent will first reach 500?\r<BR>\n" );
document.write( "\n" );
document.write( "2 -  Write down the value of the scale factor for the exponential<BR>\n" );
document.write( "model. Use this to find the percentage increase in the total<BR>\n" );
document.write( "number of emails sent?<BR>\n" );
document.write( "------<BR>\n" );
document.write( "I'll use t for the # of months.<BR>\n" );
document.write( "Also, use * (Shift 8) for multiply.  x is often used elsewhere.<BR>\n" );
document.write( "-------<BR>\n" );
document.write( "u = 20*(1.8)^t<BR>\n" );
document.write( "---<BR>\n" );
document.write( "1 -  find the month in which the exponential model predicts that the total<BR>\n" );
document.write( "number of emails sent will first reach 500?<BR>\n" );
document.write( "500 = 20*(1.8)^t<BR>\n" );
document.write( "25 = 1.8^t<BR>\n" );
document.write( "log(25) = t*log(1.8)<BR>\n" );
document.write( "t = log(25)/log(1.8)<BR>\n" );
document.write( "t =~ 5.48 months<BR>\n" );
document.write( "--> the 5th month<BR>\n" );
document.write( "==============================\r<BR>\n" );
document.write( "\n" );
document.write( "2 -  Write down the value of the scale factor for the exponential<BR>\n" );
document.write( "model. Use this to find the percentage increase in the total<BR>\n" );
document.write( "number of emails sent?<BR>\n" );
document.write( "Increase from when to when?<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );