I can't math like I used to. Could someone tell me how to calculate something from the gaming world? A character has a certain amount of hitpoints and armor which reduced incoming damage by a percentage and I want to calculate how much effective hitpoints that results in. A web search only yielded way too complicated explanations for special cases, coding and such. All I can spontaneously figure out is that 50% damage reduction doubles HP, so it's a bit of an inverse, but when I tried making a formula out of that, it didn't quite work.