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## Homework Statement

Radioactive iodine (131-I) has a half life of 8 days. How long does it take for iodine to be reduced by factor of 100?

## Homework Equations

N(t)=N(o)e

^{-kt}

k=ln100/t

_{1/2}

## The Attempt at a Solution

N(t)=N(o)e

^{-kt}

N(t)/N(o)=e

^{-ln(100/8)t}

Now I'm stuck. I would think to to take the ln of both sides, but there isn't any values given for N(t) or N(o). Also, the value of k I'm pretty sure is right...Any confirmation on this?

Thanks alot for your help :)