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March 1, 2015

March 1, 2015

Posted by **Lee** on Sunday, November 8, 2009 at 7:47pm.

a) What is the half-life of the substance?

? years

(b) How long would it take the sample to decay to 10% of its original amount?

? years

- Calc -
**drwls**, Sunday, November 8, 2009 at 7:59pma) Let the half life in years be H

2^-(1/H) = 0.935

Solve that for H.

-1/H log 2 = log 0.935

-1/H = -0.09696

H = 10.31 years

b) Solve 2^-(t/10.31) = 0.10

t will be the time required to decasy to 10% activity

You could also solve

(0.935)^t = 0.1

The answer should be the same either way you do it: about 30 years.

- Calc -
**Lee**, Sunday, November 8, 2009 at 8:22pmThank you!

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