document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=117581>Question 117581</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0534954146/algebrahomeworkh>Fundamentals of Alg and Trig</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> Hello, I was wondering if there is anyone that could help me with this problem. Any help at all would be greatly appreciated.<BR>\n" );
document.write( "THanks\r<BR>\n" );
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document.write( "A drug is eliminated from the body through urine. Suppose that for a dose of 10 milligrams, the amount A(t) remaining in the body t hours later is given by A(t)=10(0.8)^t and that in order for the drug to be effective, at least 2 milligrams must be in the body.<BR>\n" );
document.write( "a) Determine when 2 milligrams is left in the body?\r<BR>\n" );
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document.write( "b)WHat is the half llife of the drug? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #85576 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=85576\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A drug is eliminated from the body through urine. Suppose that for a dose of 10 milligrams, the amount A(t) remaining in the body t hours later is given by A(t)=10(0.8)^t and that in order for the drug to be effective, at least 2 milligrams must be in the body.<BR>\n" );
document.write( "a) Determine when 2 milligrams is left in the body? <BR>\n" );
document.write( "Let A(t) = 2 and solve for \"t\":<BR>\n" );
document.write( "2 = 10(0.8)^t<BR>\n" );
document.write( "0.2 = (0.8)^t<BR>\n" );
document.write( "Take the log of both sides to get:<BR>\n" );
document.write( "log0.2 = tlog(0.8)<BR>\n" );
document.write( "t = [log0.2/log0.8]<BR>\n" );
document.write( "t = 7.2126 hrs<BR>\n" );
document.write( "-----------------------<BR>\n" );
document.write( "b)WHat is the half life of the drug?<BR>\n" );
document.write( "Let A(t) = (1/2)A(0) and solve for \"t\":<BR>\n" );
document.write( "(1/2)(A(0)) = A(o)(0.8)^t<BR>\n" );
document.write( "0.5 = (0.8)^t<BR>\n" );
document.write( "Take the log:<BR>\n" );
document.write( "t = [log0.5]/[log0.8] = 3.1063 hrs<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" );