<PRE><B>Question 111072</B>
A radioactive element sodium-24 has a half-life of 14 hrs. and is used to help locate obstructions of blood flow. A procedure requires 0.9 grams and is scheduled to take place in 43 hours. The rate of decay of sodium-24 is 5%.
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A(t) = Ao(1/2)^(t/14)
0.9 = Ao(1/2)^(43/14)
0.9 = Ao[11.896189...]
Ao = 7.5654... grams (the amount you need now to have 0.9 grams in 43 hours)

What is the minimum amount of sodium-24 that must be on hand now? 
7.5654...grams
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At least ____ years. (Answer should be accurate to two decimal places.) 
Question: Years to do what?
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Cheers,
Stan H.

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