In Japan, the order of multiplication is discussed online.

How much does it cost to buy five apples for 50 yen each?

At school, 50x5 = 250 is correct, and writing 5x50 = 250 is incorrect.

Many mathematicians say that the order of multiplication is meaningless, but some school teachers do not change their mindset. :0point:

@mayuutann This is a horrible thing to do. Japan just lost generations worth of mathematicans with this because there are actually a bunch of kids good in math what make leisure from experimenting with their knowledge making ways to themselves to build new approaches.

This is such a wasted potential :blobcatoh:

Albert Einstein was actually a kid like this as I learned from his biography. He started playing and then mastering math and wondering about the world's rules in a young age and actually getting terrible qualities in a punishing school system.

@RealPurrplenekoboi >Japan just lost generations worth of mathematicans

Yeah, I think so, too. :ohdear:
Yeah, I respect Einstein too. :blobderpy:

@mayuutann Anyone who considers themselves to be a mathematician should be aware that multiplication is, by definition, commutative. As such, there's no difference whether you write the one or the other factor first.

And if they were to expect people to correctly categorize by multiplier and multiplicand, they should only allow 5 ⋅ 50, since the multiplication is defined as 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑟 ⋅ 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑐𝑎𝑛𝑑, whereas the first denotes the count and the second one the value being multiplied. :blobnerd:

@mayuutann Then, again, the order varies by culture, according to Wikipedia. So it might actually be correct in Japan to use 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑐𝑎𝑛𝑑 ⋅ 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑟...

@mezzodrinker Yeah, I know that the order varies by culture. Is it wrong if you write the other way in your country, too?

@mayuutann Honestly, I'm pretty sure that teachers over here couldn't care less. They would certainly teach it in a specific way (the 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑟 ⋅ 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑐𝑎𝑛𝑑 order, if I recall correctly) but if you opt to do it differently, they will probably not mind.

Or at least I don't recall this ever being a topic of discussions back when I was at school.

@mayuutann Yeah; I heard that Japan is a lot more traditional and disciplined about education.

@mezzodrinker There are many rules that are not essential. :awoo_grill:

@mayuutann @mezzodrinker
I was tought that the order doesn't matter. Math is math and shouldn't be a cultural thing to punish people.

@ludibrium @mayuutann
> The order doesn't matter.
It does, but only if you add semantics. Raw maths doesn't care about the order of a multiplication's operands.

> Math is math and shouldn't be a cultural thing to punish people.
Yeah. Still, school maths ⊂ maths

@mezzodrinker @mayuutann
@ludibrium @mayuutann
> The order doesn't matter.
It does, but only if you add semantics. Raw maths doesn't care about the order of a multiplication's operands.


> Math is math and shouldn't be a cultural thing to punish people.
Yeah. Still, school maths ⊂ maths

@mezzodrinker @mayuutann
>multiplication is by definition commutative
No. When multiplication is generalized, order matters. See matrix multiplication.

I do agree that nitpicking order in elementary school is stupid though.

@passenger @mayuutann ...but wouldn't a generalized multiplication be called product instead?

Anyway, I see your point, and you're right.

@mezzodrinker @mayuutann
unless money is a group on which integers have a right-action (like scalar multiplication on vectors, but you write the scalar on the right instead of on the left).

@mayuutann Wow. That's a great way to stopping the kids from thinking logically and understanding what multiplication really is, on a fundamental level.

@snowyfox maybe no. At least I've never heard that. maybe some teachers mind only order of multiplication. 🤔

@mayuutann that's super silly, I hope they only do that on lower grades or something
@shpuld @mayuutann butyou: "why did you write the multiplication the wrong way? please redo the report"

@shpuld They only do that on primary school. But people worry about that children will hate math. Because it ’s not wrong, but it ’s wrong. :ohdear:

@mayuutann it's wrong to teach that the order matters

@angristan @mayuutann i'll be writing 5x50 = 250 on anything I publish from here on out, just to rock the boat.

@resist1984 @angristan hahaha, but it seems that the order of teaching is different depending on the country. So that maybe be correct. 😅

@mayuutann Synonyms or near-synonyms, were the only reason I didn't get max scores on my English vocabulary tests here. Because our teach absolutely refused to accept the answer if we didn't memorize the exact translation in the book.

For example if I translated a word into "waste" or "garbage", instead of "trash", which was written in the book, I'd lose that point.

Some teachers are just really fucking strict about the most pointless things and it sucks.

We had one teacher who kept nagging about the order of multiplication too, but at least he didn't subtract actual points for it. He'd usually write an annoying comment next to the answer every time we "messed" up the multiplication order though.
@mayuutann Knowing Japan, I guess your teacher are pretty strict in general?

@quad Ahh, he isn't my teacher. This is a discussion that is currently a hot topic in Japan. 😅

@mayuutann Ah okay, I'm glad I never had a teacher who actually subtracted points for something like that in maths. I did in English though.
@mayuutann That sounds like enforcing a style guide. I could see it making it faster to grade tests if all the answers will look more uniform.

@brad yes. Perhaps the teachers who care about the order is to let them do what they taught. :blobmelt:

@mayuutann IIRC in Japan you're not allowed to prove your superior wrong, so I'm not surprised.

I mean both have good reasons.
One the one hand: Multiplication within the complex numbers is commutative and therefore the result doesn't change. So the order doesn't matter.
On the other hand: There are many other operators and structures on which multiplication is not commutative (e.g. matrix-matrix multiplication).

Of course for just multiplying with "normal" numbers it's fine to ignore order but in a strict technical sense it doesn't, it just doesn't change the result.

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