When I use math in secret, it is problems to figure out an average. If I eat 16 Hersey Kisses today, and I do this every other day for the entire week then I've eaten about 9 pieces of chocolate a day this week. I guess it's not a secret when I use math but I find myself sort of averaging things that I do out like that. If I want to buy a car that won't break down right away, I'll need maybe $8,000-$10,000, so that would be $278 a month that I'd need to save for three years. But there is no way I could make that much money until I get a real job that is not babysitting so I'd find a cheap, broken $2,000 car on Craigslist. That would be $167 a month for a year, and that is much more reasonable.
I don't really think about it that much, but I do this sort of math a lot. I'm not even sure if it has a name, but it helps me plan I guess, or see what I've eaten.