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September 19, 2014

September 19, 2014

Posted by **Kim** on Friday, March 6, 2009 at 12:08am.

1.What is the half-life of the element?

2.How long will it take for a sample of 100 mg to decay to 46 mg?

- Calculus-Modeling Equations -
**drwls**, Friday, March 6, 2009 at 12:23amA(t)= Ao* (1/2)^(t/h)

where h is the half life.

A/Ao = 1-0.39 = 0.61

0.61 = (1/2)^(420/h)

log 0.61 = (420/h) log (1/2)

420/h = 0.71312

h = 589 days

When 100 mg becomes 46 mg of radioactive material, A/Ao = 0.46

0.46 = (1/2)^(t/589)

t/589 = log(0.46)/log(0.50)= 1.1203

t = 660 days

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