document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=195268>Question 195268</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0321233832/algebrahomeworkh></A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> STANBON You helped me with this problem:  <BR>\n" );
document.write( "The level of thorium in a sample decreases by a factor of one-half every 2 million years. A meteorite is discovered to have only 8.6% of its original thorium remaining. How old is the meteorite? I already have the answer, but need to know<BR>\n" );
document.write( "  What does Ao represent? Do you know what the value of Ao? What does t represent? What are the units of t?  Thanks!<BR>\n" );
document.write( "  <BR>\n" );
document.write( "-----------<BR>\n" );
document.write( "A(t) = Ao*(1/2)^(t/2*10^6)<BR>\n" );
document.write( "-----------------------<BR>\n" );
document.write( "0.086Ao = Ao*(1/2)^(t/(2 million))<BR>\n" );
document.write( "(1/2)^(t/2 million) = 0.086<BR>\n" );
document.write( "Take the log to get:<BR>\n" );
document.write( "(t/2 million) = log(0.086)/log(1/2) = 3.53951953<BR>\n" );
document.write( "t = (2 million)*(3.53951953)<BR>\n" );
document.write( "t = 7,079,039.06 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #146460 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=146460\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> You helped me with this problem: <BR>\n" );
document.write( "The level of thorium in a sample decreases by a factor of one-half every 2 million years. A meteorite is discovered to have only 8.6% of its original thorium remaining. How old is the meteorite? I already have the answer, but need to know<BR>\n" );
document.write( "What does Ao represent? Do you know what the value of Ao? What does t represent? What are the units of t? Thanks!\r<BR>\n" );
document.write( "\n" );
document.write( "-----------<BR>\n" );
document.write( "A(t) = Ao*(1/2)^(t/2*10^6)<BR>\n" );
document.write( "A(t) is the amount of material you have at time \"t\".<BR>\n" );
document.write( "Ao is the amount of material you have in the beginning: at time t=0<BR>\n" );
document.write( "In your problem you do not know the amount at time t=0, so you<BR>\n" );
document.write( "do not know Ao.  But since you have it on both sides of the equation,<BR>\n" );
document.write( "it cancels out.<BR>\n" );
document.write( "In your problem t represets the number of years the thorium has<BR>\n" );
document.write( "been around (presumably in the meteorite).<BR>\n" );
document.write( "-----------------------<BR>\n" );
document.write( "0.086Ao = Ao*(1/2)^(t/(2 million))<BR>\n" );
document.write( "(1/2)^(t/2 million) = 0.086<BR>\n" );
document.write( "Take the log to get:<BR>\n" );
document.write( "(t/2 million) = log(0.086)/log(1/2) = 3.53951953<BR>\n" );
document.write( "t = (2 million)*(3.53951953)<BR>\n" );
document.write( "t = 7,079,039.06 years<BR>\n" );
document.write( "==============================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );