What does adhd have to do with anything?
this post was submitted on 18 Oct 2024
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ADHD is sometimes used as a catchall to mean a set of behaviors that does not coincide with the majority at school or work. Ive met a bunch of people on ADHD medicine, but it was usually because they wanted to force themselves to be good at or like something they didnt want to do normally.
In this case its called ADHD because the student has found their own way to solve it despite the method the teacher is teaching and that the rest of the class uses.
Mental arithmetic is all little tricks and shortcuts. If the answer is right then there's no wrong way to do it, and maths is one of the few places where answers are right or wrong with no damn maybes!
Well, there are certainly wrong ways to arrive at the answer, e.g. calculating 2+2 by multiplying both numbers still gets you 4 but that is the wrong way to get there. That doesn't apply to any of the methods in the post though.
I would have done 10+6, but that's effectively the same thing as the OP.
Aside from literally counting, what other way is there to arrive at 16? You either memorize it, batch the numbers into something else you have memorized, or you count.
Am I missing some obvious 'natural' way?
I'd argue memorizing it is the natural way, at least if you work with numbers a lot. Think about how a typist can type a seven letter word faster than a string of seven random characters. Is that not good proof that we have pathways in our brain that short circuit simpler procedural steps?
Theres more complicated ways for sure, but I think we have identified all the simple ones. Could break it into twos I guess.
Has nothing to do with ADHD.
Common core made an effort to teach kids to think about numbers this way and people flipped the fuck out because that wasn't how they were taught. Still mad about that.
The problem with common core math was not that they taught these techniques. It's that they taught exclusively these techniques. These techniques are born from the meta manipulation of the numbers which comes when you have an understanding of the logic of arithmetic and see the patterns and how they can be manipulated. You need to understand why you can you "borrow" 1 from the 7 or the 9 to the other number and get the same answer, for example. It makes arithmetic easier for those who do it, yes, but only because we understand why you are doing it that way.
When you just teach the meta manipulation, the technique, without the reason, you are teaching a process that has no foundation. The smarter kids may learn to understand the foundational logic from that, but many will only memorize the rules they are taught without that understanding of why and then struggle to build more knowledge without that foundation later.
Math is a subject where each successive lesson is built on the previous lessons. Without being solid on your understanding, it is a house of cards waiting to fall.
To add to this, people come up with math tricks all the time but you then have to check it against the manual method, and often multiple times with different numbers, before you can connect the manual process to the trick for later use.
In my opinion I don't think you can teach just the trick side of it, if thats what common core is.
There's ~~people~~aliens who would add 9+7 instead of 10+6 or 8+8 in their heads?
I do, because 9 plus anything is just a 1 in front of the other digit minus 1.
Weirdly enough, I just thought about using the methods here for the first time in my life earlier today. Weird.
9 plus anything is just a 1 in front of the other digit minus 1
This is also how it works in my head, but isn't it the same as the other guy was saying, 10+6?
The difference would just be how you think of the process. I sometimes shuffle around the numbers to make math easier, but the shortcut for adding 9s just feels different. Instead of 9+7 = 10 + 6, it's more like 9+7 = 17-1. It feels less like solving it with math and more like using a cool trick, since you didn't really use addition to solve the addition problem.
Sort of, same numbers different logic. Its like mixing up the order of operations. You could learn both tricks but it seems redundant if they do the same thing. Like having two of the same hammer.
Goes to show how little our education system is teaching kids to understand what you're supposed to be learning.
You are literally responding to a comment about how our education system is now teaching kids to understand the basic fundamentals of mathematics instead of just rote learning methods.
I'm drunk and meant my comment to reflect more on the past rather than the present
8+8 and 8X2 are literally the exact same thing, why did they feel the need to make that an extra step?
Probably because they were forced to memorize times tables, but not arithmetic so they wanted to show where they are leveraging that memorization from
Whatever number is closest to 10 steals enough to make itself 10. Same goes for hundreds, thousands, whatever. Get your round numbers first, add in the others later. All numbers must become 10. In a pinch, a number may become a 5, but if so, it's really just become a half-10, and it should feel bad about itself that isn't a full 10 yet.
9 is 3+3+3, 7+3 is 10, 3+3 is 6, 6+10 is 16. I'm also a fucking heathen.
I explained to a teacher one time this as my method, the get to ten version, and she looked confused as hell like why would anyone do that. She was cool with it though, gave me a whatever works for you kind of response.
Let's make that 9 a 10 because it's good enough, it's smart enough, and goshdarnit people like it. Also, I don't wanna add with a 9. So 10 + 7 would be 17, but we added 1 to the 9 to make it 10 so now we take 1 away, 17 - 1 = 16.
ezpz
9 plus a number? No. 10 plus a number, minus 1. Yis.
Okay this is nice and all but how do people do 3974* 438 mentally, without paper? And bigger and some outright freaks seem to do it in an instant
Not any great easy way I can think of to do that one but I would attempt to do 400 by 3974 and then add chunks of 438 x 10 or x5 until I got really close and then add individual blocks.
So like 400 by 3974, you can round to 4000 and remove 4 x 26 = 104 after doubling 4000 twice. So we have 4000 to 8000 to 16000 remove 104 is 15896, add zeros is 1,589,600. Forget all other numbers but this one.
We are missing 38 x 3974. We can do the same round and remove trick to add 10 x 3974 by changing it to 10 x 4000 - 10 x 26. We need four of those though, so we can double it and turn from 40000 - 260 to 80000 - 520 and then 160,000 - 1040 or 158,960. Need to remove 2 x 3974 though, so remove 8000 and add 52 so 151,012.
Hopefully ive been able to keep that first number fresh in my head this whole time, which involves repeating it for me, and I'd add 1,589,600 and 151,012. Add 150000 and then 1,012 so 1,739,600 and then 1,740,612.
That all said, I make way more mistakes than a calculator, and I was off by 400 or so on my first run through. Also its really easy to forget big numbers like that for me. I'd say if you gave me ten of these to do mentally I'd get maybe 2 correct.
Depends how much neuron density you have in the part of the brain that handles this. It's mostly about memory, being able to accurately and quickly remember all the little steps you have already done and what the results of those steps were. Then just keep going one digit pair at a time keeping in mind all the results so you can deal with the carry overs.
But the whole reason we can focus on teaching everyone shortcuts for smaller math now is because we do literally always have a calculator on us now. So while it's still good to know how to do bigger math more efficiently, you'll never catch up to a calculator anymore. It's more important that they know the foundational concept well enough to move on to the next step now rather than practicing doing big math faster and faster. Can leave that to the individuals with talent in the area.