<PRE><B>Question 481950</B>
 If sodium-24 has a half-life of fifteen hours, and you have a sample that contains 15 kg of sodium-24, how much would remain after twelve hours? 
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A(t) = Ao(1/2)^(t/k) where k is the half-life
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A(12) = 15(1/2)^(12/15)
= 15*0.57435
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= 8.6152 kg
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Cheers,
Stan H.</PRE>