document.write( "Question 944489: Radioactive strontium-90 is used in nuclear reactors and decays according to A = Pe^-0.0248t where P is the amount at t = 0, and A is the amount remaining after t years. Find the half-life of strontium-90; that is, find t so that A=0.5P. \n" ); document.write( "

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Radioactive strontium-90 is used in nuclear reactors and decays according to A = Pe^-0.0248t where P is the amount at t = 0, and A is the amount remaining after t years.
\n" ); document.write( " Find the half-life of strontium-90; that is, find t so that A=0.5P.
\n" ); document.write( ":
\n" ); document.write( "assume P = 1 and A = .5
\n" ); document.write( " $\"e%5E%28-0.0248t%29+=+.5\"$
\n" ); document.write( " $\"ln%28e%5E%28-0.0248t%29%29+=+ln%28.5%29\"$
\n" ); document.write( ":
\n" ); document.write( "log equiv of exponents
\n" ); document.write( "-.0248t*ln(e) = ln(.5)
\n" ); document.write( ":
\n" ); document.write( "ln of e =1, find ln of .5, so we have
\n" ); document.write( "-.0248t = -.693
\n" ); document.write( "t = $\"%28-.693%29%2F%28-.0248%29\"$
\n" ); document.write( "t = 27.949 ~ 28 years is the half life of Strontium-90
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