Yeah, I was sent a link to a similar site yesterday (timed mental arithmetic/algebra), and was thinking exactly the same thing: divided by types, half the probl

Yeah, I was sent a link to a similar site yesterday (timed mental arithmetic/algebra), and was thinking exactly the same thing: divided by types, half the problems I could do instantly with almost no thought, but the other half, regardless of how easy, took a few seconds. I noticed that with, for example, multiplication, I have a set of rote-learned answers for calculations that aren't 2, 5 or *10, and if the answer isn't one of those answers, I'll get the closest answer I can remember, and work back/forward from that. It's entirely habit, and I can't stop myself doing it. Algebra as well, I always have a moment where I swap parts of the equation in my head; even if it's utterly simple, there's still a noticeable cognitive step.