<PRE><B>Question 194634</B>
The level of thorium in a sample decreases by a factor of one-half every 2 million years. A meteorite is discovered to have only 8.6% of its original thorium remaining. How old is the meteorite? 
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A(t) = Ao*(1/2)^(t/2*10^6)
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0.086Ao = Ao*(1/2)^(t/(2 million))
(1/2)^(t/2 million) = 0.086
Take the log to get:
(t/2 million) = log(0.086)/log(1/2) = 3.53951953
t = (2 million)*(3.53951953)

t = 7,079,039.06
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Cheers,
Stan H.
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