I'm currently working on some Differential Calculus, and I'm having a bit of trouble with the following question.
The half-life of an isotope is 150 years. Use this information to determine the differential equation that describes the mass as a function of time. In other words m' = km where k is a constant and m(t) is the mass after t years.
Use the information given to find k, then solve this equation. Use the solution to determine how long it takes for an initial amount to decay to 15% of the original.
For what I know so far, I know little to nothing on the matter. My professor has failed to elaborate on the subject whatsoever, and I've been googling this to try and answer it.
I think I'm supposed to use this question, but I'm not sure if it's the right one...