Math is cool, I've had way too much of it (Calc I - IV, Linear Algebra and Differential Equations) It is truly amazing to me the elegance of the physical world sometimes. Simple things like the revolution of the Earth around the Sun can be described and predicted with simple formulas...Oh shut up!
I use a lot of math in my job...rates of change are all Differential Equations...how much time does it take a chemical reaction to occur, how fast are the chemicals being reacted and how much heat do you need to add...all over the correct periods of time. The trick is that the quantities are changing...as reactions occur the chemicals change from one form to another meaning you have less and less of one thing and more and more of another. This means the physical properties of the batch change too...Again though simple equations can simulate really complex ideas.
Painting/customizing is a good one. One I've tried and enjoyed with some limited success, but I look at some of the paint jobs I've done and they are a tad sloppy. It was sort of a mix of me being a novice and rushing. I wish I had the time to get into that again because it is relaxing and a rewarding part of the hobby IMO