this post was submitted on 27 Nov 2025
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[–] marcos@lemmy.world 39 points 1 day ago (2 children)

Some people insist there's no "correct" order for the basic arithmetic operations. And worse, some people insist the correct order is parenthesis first, then left to right.

Both of those sets of people are wrong.

[–] SkyeStarfall@lemmy.blahaj.zone 3 points 1 day ago (1 children)

I mean, arithmetic order is just convention, not a mathematical truth. But that convention works in the way we know, yes, because that's what's.. well.. convention

[–] marcos@lemmy.world 0 points 1 day ago

Social conventions are real, well defined things. Some mathematicians like to pretend they aren't, while using a truckload of them; that's a hypocritical opinion.

That's not to say you can't change them. But all of basic arithmetic is a social convention, you can redefine the numbers and operations any time you want too.

[–] MotoAsh@piefed.social 8 points 1 day ago* (last edited 1 day ago) (3 children)

Hopefully you can see where their confusion might come from, though. PEMDAS is more P-E-MD-AS. If you have a bunch of unparenthesized addition and subtraction, left to right is correct. A lot of like, firstgrader math problems are just basic problems that are usually left to right (but should have some extras to highlight PEMDAS somewhere I'd hope).

So they're mostly telling you they only remember as much math as a small child that barely passed math exercizes.

[–] SpaceCadet@feddit.nl 8 points 1 day ago* (last edited 1 day ago) (2 children)

If you have a bunch of unparenthesized addition and subtraction, left to right is correct

If you have a bunch of unparenthesized addition and subtraction, left to right doesn't matter.

1 + 2 + 3 = 3 + 2 + 1

[–] kuberoot@discuss.tchncs.de -1 points 20 hours ago (1 children)

If you have a bunch of unparenthesized addition and subtraction, left to right doesn't matter.

Right, because 1-2-3=3-2-1.

[–] howrar@lemmy.ca 1 points 9 hours ago

You flipped the sign on the 3 and 1.

[–] MotoAsh@piefed.social 3 points 1 day ago (1 children)

True, but as with many things, something has to be the rule for processing it. For many teachers as I've heard, order of appearance is 'the rule' when commutative properties apply. ... at least until algebra demands simplification, but that's a different topic.

[–] SpaceCadet@feddit.nl 3 points 1 day ago (2 children)

something has to be the rule for processing it

Well the rule is: any order goes. Summation is commutative.

[–] MotoAsh@piefed.social 4 points 1 day ago* (last edited 1 day ago)

No, you completely misunderstood my point. My point is not to describe all valid interpretations of the commutative property, but the one most slow kids will hear.

OFC the actual rule is the order doesn't matter, but kids that don't pick up on the nuance of the commutative property will still remember, "order of appearance is fine".

[–] Quatlicopatlix@feddit.org 2 points 1 day ago

Yes thank you! If you have a sum it is really great to order it in a way that makes it better to ad in your head and i think that lots of people do that without thinking about it. X=2+3+1+6+2+4+7+5 X=2+3+5+4+6+7+1+2 X=5+5 + 10 +7+1+2 X=10 + 10 + 7+3 X=10 + 10 + 10

[–] Feathercrown@lemmy.world 5 points 1 day ago

PE(MD)(AS)

Now just remember to account for those parentheses first...

[–] orbitz@lemmy.ca 2 points 1 day ago

Huh I just remembered the orders of arithmetic but parentheses trump all so do them first (I use them in even the calculator app). Mean I assume that's that that says but never learned that acronym is all. Now figuring out categories of words;really does my noodle in sometimes. Cause some words can be either depending on context. Math when it's written out has (mostly) the same answer. I say mostly because somewhere in the back of my brain there are some scenarios where something more complicated than straight arithmetic can come out oddly but written as such should come out the same.