It took me 3 years to pass HS algebra because the coaches/part-time math teachers didn't like the way I solved problems. I got the right answers. But the way I got them was wrong apparently.
this post was submitted on 18 Oct 2024
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If your teacher gets mad about breaking an addition problem into easier problems, then that teacher should be fired. Phony tale.
If anything, these are exactly the techniques that "New Math" was supposed to teach. Your brain doesn't work math the same way as a computer. People who are good at math tend to break the whole thing down into simple pieces like this. New Math was developed by studying what they did and then teaching that to everyone.
I tend to add 9 to things by bumping the tens digit up by one (7 becomes 17) and then subtracting 1 (17 becomes 16).
Most of the arguments against New Math tended to prove the point; our mathematical education was in dire need of fixing.
The second method is very chemistry-like. I do that too naturally
I thought that too, 9 is like a halogen, it wants to resolve to 10 anyway it can like fluorine wants one last electron. So allow the 9 to rip one off of the neighboring numbers and then perform the calculation.
I’ve never really liked the anthropomorphic description of chemical bonding, but maybe it’s actually similar to the addition thing. On the one hand, we can say 9 wants to resolve to 10 and takes a 1, and on the other hand we could say there are a bunch of different ways we could rearrange these numbers but the end result is the same as if we resolve 9 to 10 first. Maybe chemical reactions are similar, so there’s a bunch of configurations that could have happened, but the end result is the same as if we had said fluorine wants that last electron
Although, electron affinity is a thing… so the analogy does break down pretty quick. Rip
Yo but hear me out. Because 7 ate(8) 9, 7 + 9 = 7
What does adhd have to do with anything?
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.
It's because it's stupid. The bottom answer is at least sort of similar to a simple rule for adding 9s. But the op is just so incredibly specific that it won't help most of the time.
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?
My mental image is squishing the 7 into the 9 but only 1 is able to be squished in, leaving 6 overflowing
For my kids, apparently some kind of number line nonsense, which is counting with extra steps.
I just memorize it. When the numbers get big, I do it like you did. For example, my kid and I were converting miles to feet (bad idea) in the car, and I needed to calculate 2/3 mile to feet. So I took 1760 yards -> 1800 yards, divided by three (600), doubled it (1200), and multiplied by 3 to get feet (3600). Then I handled the 40, but did yards -> feet -> 2/3 (40 yards -> 120 ft -> 80 ft). So the final answer is 3520 ft (3600 - 80). I know the factors of 18, and I know what 2/3 of 12 is, so I was able to do it quickly in my head, despite the imperial system's best efforts.
So yeah, cleaning up the numbers to make the calculation easier is absolutely the way to go.
A mile is 1760 yards, and there are three feet in a yard. Therefore, 1760 feet is 1/3 of a mile, and 2/3s of a mile is 3520 feet.
The imperial system is actually excellent for division and multiplication. All units are very composite, so you usually don't need to worry about decimals.
Yup. The reason I went with yards was because I knew 1760 was closer to a nice multiple of 3 than 5280 (neither 5200 or 5300 is a multiple of 3; I'd have to go to 5100 or 5400).
But yeah, imperial works pretty well for multiplication and division, it's just not intuitive for figuring out the next denomination. Why is a mile 1760 yards instead of 1000 or 1200? Why is it 5280 feet instead of 6000? Why is a cup 8 oz instead of 6 (nicer factors) or 10? Why is a pound 16 oz instead of 8 oz like a cup would be (or are pints the "proper" larger unit for an oz)?
The system makes no sense as a tiered system, but it does make calculations a bit cleaner since there's usually a whole number or reasonable fraction for common divisions. Base 10 sucks for that, but at least it's intuitive.
Metric would be perfect if 10 wasn't such a dog shit number to base our counting off of. Sure it works for dividing things in half, but how often do you need to break something down into fifths? Halves, thirds, and quarters are 90% of typical division people do, with tenths being most of the rest since 10 is that only number that our base system actually works with.
As in, visualizing a number line in their heads? Or physically drawing one out?
I could see a visual method being very powerful if it deals in scale. Can you elaborate on that? Or, like try to understand what your kids' 'nonsense' is?
I think my 7yo visualizes the number line in their head when there's no paper around, but they draw it out in school. I personally don't understand that method, because I always learned to do it like this:
7372
+ 273
=====
And add by columns. With a number line you add by places, so left to right (starting at 7372, jump 2 hundreds, 7 tens, and 3 ones), whereas with the above method, you'd go right to left, carrying as you go. The number line method gets you close to the number faster (so decent for mental estimates), but it requires counting at the end. The column method is harder for mental math, but it's a lot closer to multiplication, so it's good to get practice (IMO) with keeping intermediate calculations in your head.
I think it's nonsense because it doesn't scale to other types of math very well.
You still haven't told me what the number line method actually is. I know how to add up the columns bud
Number line is something like this:
100 | 200 | 300 ... | 10 | 20 | 30 ... | 1 | 2 | 3
==================================================
You write out the numbers that are relevant and hop by those increments. So for 7372 + 273, you'd probably start at 7000, hop 100 x 5 (3 for 372 and 2 for 273), hop 10 x 14 (7 for 72 and 7 for 73), and so on. It's basically teaching you to count in larger groups.
To multiply, you count by the multiple (so for 7 x 3, you'd jump in groups of 3).
This article seems to explain it. I didn't learn it that way, so I could be getting it wrong, but it seems you do larger jumps and and the jumps get smaller as you go. I think it's nonsense, but maybe it helps some kids. I was never a visual/graphical learner though.
So, are you just talking about number lines in general?
I learned how to use those in grade school too. 20+ years ago. But the way you phrased it made me think there was more to it. Calling it nonsense is.. shocking.
I'm also in 10+6 gang, and it's more universal, as in a decimal system you will always have a 10 or 100 to add up to, and a "pretty" 8+8 is less usual
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?
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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!
That's also all common core is. Instead of teaching the line up method which requires paper and is generally impractical in the real world, they teach ways to do math in your head efficiently.
What is "common core" and what is the "line up method"?
Unless you consider probabilities. That's a very strange field—you can't objectively verify it.
You can't objectively verify anything in mathematics. It's a formal system.
Once you start talking about objective verification, you're talking about science not math.
Unsolved problems do not all fall into binary outcomes. They can be independent of axioms (the set of assumptions used to construct a proof).
I like your funny words, mathemagic man
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Has nothing to do with ADHD.
Wouldn't say nothing to do with.
Many neurodivergent students find themselves in situations where they haven't fully absorbed the taught material. Many of them end up figuring problems out themselves, with varying degrees of creativity and success
Neurotypical students do the same thing. It’s not like every neurotypical will internalize every piece of material they are taught.
Yup, I'm most likely neurotypical (never been diagnosed either way, just never had issues w/ traditional learning), and I generally ignored the teacher and did things my own way. I was always really good at math, so the teacher's way was usually less efficient for me, so once I understood the operation, I'd create shortcuts.
We'd go over the same material a lot, so I'd usually just do homework while the teacher taught some new way to do the same operation. I'd get marked down for doing it differently from the instructions, but I'd get the answer right.
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