So for some reason people are under the impression that a 20/20 wand + 20/20 focus gives you 40/40.
I knew there was something wrong with this assumption because if I flip a coin twice the odds of me getting heads once is not 100%.
50% + 50% != 100%
You can't simply add probabilities like this. Since my stats class was so long ago I couldn't come up with the answer off the top of my head. So I looked it up and it seems like this is the answer:
p(Either A or B or both happens) = p(A happens) + p(B happens) - p(Both A and B happen)
and p(Both A and B happening) = p(a) x p(b)
works out to 20% + 20% - 4% = 36%. I actually thought it would be lower.
So the final word on 20/20 wand + 20/20 focus give you a 36/36 !