You guys will be happy to know, and/or not care, that ((H + H * (R / 100)) - P) / (H + H * (R / 100)) = (H - (P *(100 / (100 + R))))/H
Here's a page saying that it is. http://www.wolframalpha.com/input/?i=%28%28H+%2B+H+*+%28R+%2F+100%29%29+-+P%29+%2F+%28H+%2B+H+*+%28R+%2F+100%29%29+%3D+%28H+-+%28P+*%28100+%2F+%28100+%2B+R%29%29%29%29%2FH
In other words, that stuff about effective health is actually true. If you want me to write out a longform proof I will.