<PRE><B>Question 146096</B>
A radioactive substance has a half-life of 2 years. 
There is 36 g to begin with. 
Write and equation for y=mass left after x=half-years. 
Then solve for 100 years. (how much of the 36 g will be left?)
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A(t) = Ao(1/2)^(t/2)
Comment: That t/2 exponent means you should multiply by 1/2 every 2-years.
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A(100) = 36(1/2)^(100/2)
A(100) = 36(1/2)^50
A(100) = 36*0.00000000000000088817842
A(100) = 0.0000000000000319744...grams
Or
A(100) = 3.197 x 10^-14 grams
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Cheers,
Stan H</PRE>