document.write( "Question 364239: What is the half-life of a radioactive substance if 2.4g decays to .80g in 40 hours? \n" ); document.write( "

Algebra.Com's Answer #259901 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"N%28t%29=N%5B0%5De%5E%28kt%29\"$
\n" ); document.write( " $\"0.8=2.4e%5E%28k%2840%29%29\"$
\n" ); document.write( " $\"e%5E%2840k%29=1%2F3\"$
\n" ); document.write( " $\"40k=ln%281%2F3%29\"$
\n" ); document.write( " $\"k=%281%2F40%29%2Aln%281%2F3%29\"$ or approximately,
\n" ); document.write( " $\"k=-0.02747\"$
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( " $\"%281%2F2%29N%5B0%5D=N%5B0%5De%5E%28kt%5BH%5D%29\"$
\n" ); document.write( " $\"kt%5BH%5D=ln%281%2F2%29\"$
\n" ); document.write( " $\"t%5BH%5D=ln%281%2F2%29%2F%281%2F40%29ln%281%2F3%29\"$
\n" ); document.write( " $\"t%5BH%5D=40%28ln%281%2F2%29%2Fln%281%2F3%29%29\"$ or approximately,
\n" ); document.write( " $\"highlight%28t%5BH%5D=25.2%29\"$ hrs \n" ); document.write( "

\n" );