> Speaking as someone who's been through 3 semesters of Calculus, and every math course up to then... I've never had that much trouble with it. I'm able to do most problems directly.
>
> One thing I've done all my life, to keep my arithmetic in shape... I keep my watch a random number of minutes fast. I'm just so used to random additions and subtractions by now I can do them without thinking about it, or visualizing anything.
>
> Right now, my watch says 6:52. I take 15 from the 52, and just read it as 6:37. It can take me a second or so when it's a weird figure to figure out the time, but I can usually nail it instantaneously.
>
> I've just practiced it, and done it so many times, I don't visualize anything... I can do most multiplications in my head. Even with upper division math like Calculus... I don't think
> nx^(n-1) when differentiating. It's just pretty instantaneous. We were all assigned so many practice problems, we could do it in our sleep.
>
> Of course, most of the math I'm doing these days, when you use simple arithmetic at all, you usually use a calculator because the numbers involved tend to have tons of figures. I'm still pretty in shape on my basic arithmetic though, I believe.
>
> Mark"NERD! NERD! NERD!"N


I think this is the way to go, if Dave wants to become good at math. Practice, practice a-n-d practice! While math ability can almost be genetic - as Wes describes it - it is also something that can be achieved from hard work.
The way I do math is that I have memorized (that's what I did in school, but I see no reason why an adult shouldn't do the same) all the simple additions, subtractions, divisions and multiplications and then use them as building blocks via the short cuts described by Travholt and gabby. By "simple", I mean 1+1, 1+2, 1+3, ... 13+15, 14+15, 15+15 (or thereabouts - and similarly for the other three).
With practise, both the belief and the visualization issues will fade.

jul"I believe"ian