document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1170810>Question 1170810</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The world population doubles every 35 years. In 1980 the population wasx 4.5 billion. Assuming that the doubling period remazins at 35years, estimate the population in the year 2120. SHOW WORK </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #795702 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=795702\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A=Ao(1+r)^35, r is the rate. A/Ao=2, since it is doubling.<BR>\n" );
document.write( "2=(1+r)^35<BR>\n" );
document.write( "ln both sides<BR>\n" );
document.write( "ln2=35*ln(1+r)<BR>\n" );
document.write( "0.0198=ln(1+r). Don't round<BR>\n" );
document.write( "raise both sides to the e power<BR>\n" );
document.write( "1.02000=1+r<BR>\n" );
document.write( "r=2.0%<BR>\n" );
document.write( "Consistent with rule of 70, which is 70/2%=35 years to double<BR>\n" );
document.write( "2120 is 40 years<BR>\n" );
document.write( "A=(1.02)^40*4.5 to get answer<BR>\n" );
document.write( "=9.936 billion.<BR>\n" );
document.write( " </SPAN>\n" );
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