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September 20, 2014

September 20, 2014

Posted by **Josh** on Tuesday, October 25, 2011 at 1:40am.

find the half life of a radioactive substance if 220 grams of the substance decays to 200 grams in 4 years?

- Pre Calculus -
**drwls**, Tuesday, October 25, 2011 at 2:14amLet the half life be T years

2^(-4/T) = 200/220 = 0.9091

(-4/T) log 2 = log 0.9091

-4/T = -0.1375

T = 29.1 years

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