this post was submitted on 11 Apr 2025
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Genuinely curious I am like 40 years old
Common core is more like this:
47+36 = ?
(break it down into smaller, easier math)
We take away the single digit numbers and add them separately:
7+6 = 13(10 and 3, hold onto these)
Then we take the two digit numbers and add them:
40+30=70
Then we add the 3 and then the ten from before (or vice-versa):
70+3 = 73
73+10 = 83
It seems convoluted to people who haven't tried it, but with a bit of practice it gets really easy to do fairly complex arithmetic in your head.
It's not hard to learn either, I'm only a couple of years younger than you and I've picked this up in the last 5 years or so, I'm much better at doing everyday math than I was when I had graduated high-school.
I don't think I was ever taught this, but that's more or less how I do arithmetic. More precisely, my mental arithmetic would transcribe to:
47 + 36 = 47 + (30 + 6) = (47 + 6) + 30 = 53 + 30 = 83
I was never taught it in school, but learned later that cutting arithmetic into chunks makes it much easier, though there is much more than one way to do that, I just used how I do it in my head, but other people might find it easier to do it other ways for sure.
I think they're essentially the same thing. I don't really have a process for what order to work in, just intuition for what will be the least friction. If it were big enough numbers I'd probably go through a second time in a different order of addition to double-check.
It's just weird that I've done a lot of math and never really thought about that process. That's why you'd ideally want any math below precalc to be taught by someone with a math education degree rather than someone who just has a math degree. When you've used the concepts you're teaching with enough regulatity that they're second nature, you have very poor intuition for which concepts will trip up someone learning for the first time.