Everyday Math

Interesting... many of the bits I've seen from Everyday Math are similar to the way I do arithmetic in my head. For 754-472, I would add 200+80+2.

Ann adds: I spontaneously did what I call "adding-up" subtraction a few years ago. I put absolutely no thought into it, but suddenly found myself looking at the bottom number, figuring out how many to add to get to the upper number, then, if I had to borrow, borrowing by adding to the bottom, instead of subtracting from the top. Instead of crossing off and rewriting above the problem--leaving everything a mess, all this method requires is a little tick mark on the summation line to signal when you have to add to the bottom number. I've been afraid to teach that to the kids, because (unlike EM), I think they should use just one algorithm, and get that one down, and not jump between a lot of different methods.

So, for your example, I'd ad 2 to get to 4, then, since I can't add to get from 7 to 5, I put a tick next to the bottom 4 and add from 7 to 15. Then add the tick mark to the 4 to turn it into a 5, and add 2 to get from 5 to 7. It's a really clean and easy way to do it.

Where EM really falls down is the inordinate time spent doing the "lattice method" for multiplication. I think they spend better than half of their multiplication time on it. And, when you start working with really large numbers, the method gets really tough to use.