SOLUTION: Radioactive radium has a half-life of 1580 years. A) (3 pts) Find the rate (constant) of decay. B) (4 pts) How long will it take for 80% of a quantity of radioactiv

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Question 729995: Radioactive radium has a half-life of 1580 years.
A) (3 pts) Find the rate (constant) of decay.
B) (4 pts) How long will it take for 80% of a quantity of radioactive radium to decay (to a level of 20% of the original amount)?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Let A = amount
let I = initial amount
let t = time in years
General decay eqaution, A=I%2Ae%28-kt%29

Starting at any I, half life of 1580 years makes %281%2F2%29%2AI=I%2Ae%5E%28-k%2A1580%29,
1%2F2=e%5E%28-k%2A1580%29
Find k.
...
.