Question

How much time must elapse for the activity of a block of cheese containing 131i to drop to 1.0% of its initial value?

Answer 1

For the answer to the question above,An = Ao (1/2)^(time/halflife)

Let us assume that the "1.0" means 1%

... .01 = (1/2)^(time/8)
or ln(.01) = (time/8) ln(.5)
or time = 8 ln(.01)/ln(.5) or time = 53.150849518 days
This is not a business question but a math or physics by the way.I hope this helps