If I 131 has a half-life of 8 days, what fraction will be left after a year?

Answer 1

k = 0.693/t_1/2. Solve for k and substitute into the below equation.
ln(No/N) = kt.
No = 100 (or any number you choose)
N = Solve for this.
k = from above
t = 365 days.
Solve for N, then 100/N = fraction remaining. Another way is to simply solve for No/N and take the inverse of that number. You should get the same answer either way. Check my work.

Answer 2

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