document.write( "Question 1187771: The half life of a sodium is 15 hours. How long does it take for 95% of a sample of this
\n" ); document.write( "isotope to decay? \n" ); document.write( "
Algebra.Com's Answer #818783 by ikleyn(52799)\"\" \"About 
You can put this solution on YOUR website!
.
\n" ); document.write( "The half life of a sodium is 15 hours. How long does it take for 95% of a sample of this
\n" ); document.write( "isotope to decay?
\n" ); document.write( "~~~~~~~~~~~~~~~~~~\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\r\n" );
document.write( "If 95% of the material decayed, it means that 5% of the material remained.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "So we write the decay equation in terms of half-life\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "    0.05 = 0.5^(t/15),\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "where \"t\" is the sough time, in hours.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Next we take the logarithm base 10 from both sides\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "    log(0.05) = \"%28t%2F15%29%2Alog%28%280.5%29%29\",\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "and we get the ANSWER\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "    t = \"%2815%2Alog%28%280.05%29%29%29%2Flog%28%280.5%29%29\" = use your calculator = 64.82892142 hours = 64.829 hours (rounded).\r\n" );
document.write( "
\r
\n" ); document.write( "\n" ); document.write( "Solved.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "------------------\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "On radioactive decay,  see the lesson\r
\n" ); document.write( "\n" ); document.write( "    - Radioactive decay problems \r
\n" ); document.write( "\n" ); document.write( "in this site.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "You will find many similar  (and different)  solved problems there.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "        Use this lesson as your handbook,  textbook,  guide,  tutorials, and  (free of charge)  home teacher.\r
\n" ); document.write( "\n" ); document.write( "        Learn the subject from there once and for all.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Also,  you have this free of charge online textbook in  ALGEBRA-I  in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The referred lesson is the part of this online textbook under the topic \"Logarithms\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Save the link to this online textbook together with its description\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-I
\n" ); document.write( "https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "to your archive and use it when it is needed.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "
\n" );