If I have an amulet that increases my magic regeneration by 50%, and another ring that increases it by 100%, do those numbers compile or build on each other?

Example, would it be 150% of my regular regeneration rate? Or would it be 50% of the original, and THEN 100% of that new number?

I feel pretty dumb right now.

Have a stop watch? It would be easy to figure out. As long as you are not in battle.

I'm pretty sure it'd be 150%.
The creation kit keeps track of a magickaratemod number.