Oh, I do it Steph's way, too, sometimes. I am inconsistent. And probably would try three different approaches before I'd believe the answer, really.

Heh. I amazed a friend of mine (Classics major) by comparing the per ounce prices of something we were shopping for. Only I did it by reading the little labels on the store shelf, where it was helpfully printed. She thought it was Math Major Mojo.

37 rounds to 40, and 52-40 is 12, then I add back in the 3 that took 37 to 40, for a total of 15.

Huh. Neat.

Brains are nifty things. I remember reading a study that was done with some poor Brazilian kids. They'd all worked at their parents market stalls since they were pretty young. When they were given a sheet of standard subtraction problems, they didn't do too well at it. But when they were asked things like, "If I wanted to buy something that cost 37, and I gave you 200, how much change would you give me?" they were generally all able to do it with no problem, generally by using some method like "100 + 50 + 10 + 3."

Hil, I do math in my head much the same way.

Too bad more people don't.

Case in point - the time I was at Borders and, for some reason, the register didn't do the math. The cashier couldn't figure out how much change to give me. We spent a fair amount of time there with him trying to figure it out. sheesh.

I'm so pleased with myself. I finished the bit of work I needed to today already. So now I have the rest of the day to work on my Electronic Publishing paper. Yay?

I think I subtract in my head the way Hil does. But that might just be because I'm reading the example and agreeing that it makes sense.

I come in here all gronky, and you're talking arithmetic?

Duck tapes head together to keep it from exploding.

Last year at a dance some students were selling pizza for $1.25. I gave them a five, and one of my own students gave me $4.75 in change.

Fortunately it was one of my science students, so I didn't feel so personally responsible, but boy, did I give him a hard time over it.

Depending on the size of the numbers involved, I either subtract like Hil does, or I round the biggest number up to the nearest 5 or 0, and add the number necessary to the smaller number, and then subtract. So 52 rounds up to 55, which took 3, so I add 3 to 37, which makes it equal 40, and then 55-40=15. I normally use the latter method with bigger numbers (3 digits or more) - makes the wrangling easier.

omg the maths.

I have eaten my lunch, and now have nothing else to do for 4.5 hours. The wait is ever the more excrutiating because I will be meeting EllenS for dinner tonight!