Originally Posted by Cubdriver

This is under the general subject heading of mathematical modeling covered in undergrad programs in Ordinary Differential Equations (ODE) courses, more commonly known as Diff-Eq. ("diffy-q"). Population growth is the usual subject, but you can use it for anything that has exponential growth rates like bacteria, cultures, temperatures, or money. The formula UAL T38 used is correct (it's a basic one) and is found here (Exponential growth wiki), but you can cook up a simple math model for anything like this as long as you know some basic facts. This topic is not all that huge, it is covered in a lecture or two at most. Once you see how it works no need to reinvent the wheel, just refresh on the correct procedure in your favorite college math book.