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Hungry 9 (lemmy.likes.cat)
submitted 2 months ago by sag@lemm.ee to c/curatedtumblr@sh.itjust.works
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[-] kryptonianCodeMonkey@lemmy.world 8 points 2 months ago

9 plus a number? No. 10 plus a number, minus 1. Yis.

[-] sugar_in_your_tea@sh.itjust.works 4 points 2 months ago

I just memorized any addition with 9 adds a 1 in front while reducing the other number by one. Same general step, but there's no 10 in my head, just 9+7 -> 16. Basically, promote the tens column while demoting the ones column. I think of it more like a mechanical scoreboard (flip one up, flip the other down) than an operation involving a 10.

If it's anything other than 9, I fall back to rote memorization, unless the number is big, in which case I'll do the rounding to a multiple/power of 10.

[-] kryptonianCodeMonkey@lemmy.world 2 points 2 months ago

Yeah that's a more accurate description of what i actually do in my head to. I'm not "adding 10", because I already would use a short hand method for adding 10 anyway to promoting the tens place or flipping the score card, as you said.

this post was submitted on 18 Oct 2024
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