What's the formula for radioactive decay?
The question is the half life of a radioactive chemical is 4 days. The initial mass of a sample is 2.5 grams, find (a) the mass that remains after 16 days, (b) the mass m(t) that remains after t days, (c) when will the mass be reduced to 0.05 grams.
There is an ideal and moral standard that the true helpers try to maintain. And we live by this code, and we will die by this code.
OK, that was a little extreme, but it was illustriative of the notion in question.