document.write( "Question 763706: in 10 years, 25% of a radioactive substance decays. What is its half-life? \n" ); document.write( "

Algebra.Com's Answer #465034 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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in 10 years, 25% of a radioactive substance decays.
\n" ); document.write( " What is its half-life?
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\n" ); document.write( "That means 75% remains
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\n" ); document.write( "The radio active decay formula
\n" ); document.write( "A = Ao*2^(-t/h), where
\n" ); document.write( "A = amt remaining after t
\n" ); document.write( "Ao = initial amt (t=0)
\n" ); document.write( "t = time of decay
\n" ); document.write( "h = half life of substance
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\n" ); document.write( "Let initial amt = 1 then resulting amt = .75
\n" ); document.write( "1*2^(-10/h) = .75
\n" ); document.write( "ln(2^(-10/h)) = ln(.75)
\n" ); document.write( " $\"-10%2Fh\"$ *ln(2) = ln(.75)
\n" ); document.write( " $\"-10%2Fh\"$ = $\"ln%28.75%29%2Fln%282%29\"$
\n" ); document.write( " $\"-10%2Fh\"$ = -.415
\n" ); document.write( "-.415h = -10
\n" ); document.write( "h = $\"%28-10%29%2F%28-.415%29\"$
\n" ); document.write( "h = +24 yrs is the half life\r
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