this post was submitted on 27 Nov 2025
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[–] JackbyDev@programming.dev 7 points 4 weeks ago* (last edited 4 weeks ago) (3 children)

They did the joke wrong. To do it right you need to use the ÷ symbol. Because people never use that after they learn fractions, people treat things like a + b ÷ c + d as

a + b
-----
c + d

Or (a + b) ÷ (c + d) when they should be treating it as a + (b ÷ c) + d.

That's the most common one of these "troll math" tricks. Because notating as

a + b + d
    -
    c

Is much more common and useful. So people get used to grouping everything around the division operator as if they're in parentheses.

[–] CannonFodder@lemmy.world 4 points 4 weeks ago* (last edited 4 weeks ago) (3 children)

Or
12 / 2(6)
And trying to argue this is 36.

[–] JackbyDev@programming.dev 8 points 4 weeks ago* (last edited 4 weeks ago) (1 children)

Now that's a good troll math thing because it gets really deep into the weeds of mathematical notation. There isn't one true order of operations that is objectively correct, and on top of that, that's hardly the way most people would write that. As in, if you wrote that by hand, you wouldn't use the / symbol. You'd either use ÷ or a proper fraction.

It's a good candidate for nerd sniping.

Personally, I'd call that 36 as written given the context you're saying it in, instead of calling it 1. But I'd say it's ambiguous and you should notate in a way to avoid ambiguities. Especially if you're in the camp of multiplication like a(b) being different from ab and/or a × b.

[–] SmartmanApps@programming.dev -3 points 1 week ago (1 children)

There isn’t one true order of operations that is objectively correct

Yes there is, as found in Maths textbooks the world over

that’s hardly the way most people would write that

Maths textbooks write it that way

you wouldn’t use the / symbol

Yes you would.

You’d either use ÷

Same same

It’s a good candidate for nerd sniping.

Here's one I prepared earlier to save you the trouble

I’d call that 36

And you'd be wrong

as written given the context you’re saying it in

The context is Maths, you have to obey the rules of Maths. a(b+c)=(ab+ac), 5(8-5)=(5x8-5x5).

But I’d say it’s ambiguous

And you'd be wrong about that too

you should notate in a way to avoid ambiguities

It already is notated in a way that avoids all ambiguities!

Especially if you’re in the camp of multiplication like a(b)

That's not Multiplication, it's Distribution, a(b+c)=(ab+ac), a(b)=(axb).

being different from ab

Nope, that's exactly the same, ab=(axb) by definition

and/or a × b

(axb) is most certainly different to axb. 1/ab=1/(axb), 1/axb=b/a

[–] JackbyDev@programming.dev 4 points 1 week ago* (last edited 1 week ago) (18 children)

Please read this section of Wikipedia which talks about these topics better than I could. It shows that there is ambiguity in the order of operations and that for especially niche cases there is not a universally accepted order of operations when dealing with mixed division and multiplication. It addresses everything you've mentioned.

https://en.wikipedia.org/wiki/Order_of_operations#Mixed_division_and_multiplication

There is no universal convention for interpreting an expression containing both division denoted by '÷' and multiplication denoted by '×'. Proposed conventions include assigning the operations equal precedence and evaluating them from left to right, or equivalently treating division as multiplication by the reciprocal and then evaluating in any order;[10] evaluating all multiplications first followed by divisions from left to right; or eschewing such expressions and instead always disambiguating them by explicit parentheses.[11]

Beyond primary education, the symbol '÷' for division is seldom used, but is replaced by the use of algebraic fractions,[12] typically written vertically with the numerator stacked above the denominator – which makes grouping explicit and unambiguous – but sometimes written inline using the slash or solidus symbol '/'.[13]

Multiplication denoted by juxtaposition (also known as implied multiplication) creates a visual unit and is often given higher precedence than most other operations. In academic literature, when inline fractions are combined with implied multiplication without explicit parentheses, the multiplication is conventionally interpreted as having higher precedence than division, so that e.g. 1 / 2n is interpreted to mean 1 / (2 · n) rather than (1 / 2) · n.[2][10][14][15] For instance, the manuscript submission instructions for the Physical Review journals directly state that multiplication has precedence over division,[16] and this is also the convention observed in physics textbooks such as the Course of Theoretical Physics by Landau and Lifshitz[c] and mathematics textbooks such as Concrete Mathematics by Graham, Knuth, and Patashnik.[17] However, some authors recommend against expressions such as a / bc, preferring the explicit use of parenthesis a / (bc).[3]

More complicated cases are more ambiguous. For instance, the notation 1 / 2π(a + b) could plausibly mean either 1 / [2π · (a + b)] or [1 / (2π)] · (a + b).[18] Sometimes interpretation depends on context. The Physical Review submission instructions recommend against expressions of the form a / b / c; more explicit expressions (a / b) / c or a / (b / c) are unambiguous.[16]

Image of two calculators getting different answers 6÷2(1+2) is interpreted as 6÷(2×(1+2)) by a fx-82MS (upper), and (6÷2)×(1+2) by a TI-83 Plus calculator (lower), respectively.

This ambiguity has been the subject of Internet memes such as "8 ÷ 2(2 + 2)", for which there are two conflicting interpretations: 8 ÷ [2 · (2 + 2)] = 1 and (8 ÷ 2) · (2 + 2) = 16.[15][19] Mathematics education researcher Hung-Hsi Wu points out that "one never gets a computation of this type in real life", and calls such contrived examples "a kind of Gotcha! parlor game designed to trap an unsuspecting person by phrasing it in terms of a set of unreasonably convoluted rules".[12]

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[–] MotoAsh@piefed.social 5 points 4 weeks ago

Well, now you might be running into syntax issues instead of PEMDAS issues depending on what they're confused about. If it's 12 over 2*6, it's 1. If it's 12 ÷ 2 x 6, it's 36.

A lot of people try a bunch of funky stuff to represent fractions in text form (like mixing spaces and no spaces) when they should just be treating it like a programmer has to, and use parenthesis if it's a complex fraction in basic text form.

[–] Feathercrown@lemmy.world 4 points 4 weeks ago (7 children)

The P in PEMDAS means to solve everything within parentheses first; there is no "distribution" step or rule that says multiplying without a visible operator other than parentheses comes first. So yes, 36 is valid here. It's mostly because PEMDAS never shows up in the same context as this sort of multiplication or large fractions

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[–] sukhmel@programming.dev 1 points 3 weeks ago (2 children)

Treat a + b/c + d as a + b/(c + d) I can almost understand, I was guilty of doing that in school with multiplication, but auto-parenthesising the first part is really crazy take, imo

[–] JackbyDev@programming.dev 1 points 3 weeks ago

That's a really odd way to parse it.

a +   b
    -----
    c + b
[–] SmartmanApps@programming.dev 0 points 1 week ago

Treat a + b/c + d as a + b/(c + d)

No don't. That rule was changed more than 130 years ago. a+b/c+d=a+(b/c)+d, Division before Addition

[–] SmartmanApps@programming.dev 0 points 1 week ago (1 children)

Because people never use that after they learn fractions,

Yes they do, because not every division is a fraction

[–] JackbyDev@programming.dev 1 points 1 week ago (1 children)
[–] SmartmanApps@programming.dev -2 points 1 week ago (1 children)

https://math.berkeley.edu/~wu/order5.pdf

I already said he was wrong about that. Quoting him saying it doesn't change that he's wrong about it

[–] JackbyDev@programming.dev 2 points 1 week ago (1 children)

Take it up with Berkeley then.

[–] SmartmanApps@programming.dev -2 points 1 week ago (1 children)

Take it up with Berkeley then

What for? You're only the second person ever to have quoted him. You're not the first person to refuse to look in Maths textbooks though 🙄

[–] JackbyDev@programming.dev 1 points 1 week ago (1 children)
[–] SmartmanApps@programming.dev -2 points 1 week ago (1 children)

Take it up with Berkeley

Says person refusing to look in Maths textbooks 😂

[–] JackbyDev@programming.dev 2 points 1 week ago (1 children)

I cannot stress this enough. If you have a problem with that, contact the author or Berkeley, not me.

[–] SmartmanApps@programming.dev -2 points 1 week ago (1 children)

I cannot stress this enough. If you have a problem with that, contact the author or Berkeley, not me

I cannot stress this enough - look in Maths textbooks, not random University blogs 😂

[–] JackbyDev@programming.dev 1 points 1 week ago (1 children)
[–] SmartmanApps@programming.dev -2 points 1 week ago (1 children)

Tell them, not me

You're the one commenting without reading Maths textbooks

[–] JackbyDev@programming.dev 2 points 1 week ago (2 children)
[–] mindbleach@sh.itjust.works 2 points 1 week ago (1 children)

You can stop humoring this broken robot. Especially when the context is 'yeah I already said this textbook is wrong, but I am better than you because you need to read this textbook.'

[–] JackbyDev@programming.dev 2 points 1 week ago (1 children)

They seem to believe that and on the 8th day God made the one true objective order of operations that all humans use and agree on.

[–] mindbleach@sh.itjust.works 2 points 1 week ago* (last edited 1 week ago) (1 children)

Except for that time the definition of division changed 130 years ago. Which is not a rule! It's notation, or syntax, or possibly sometimes a rule. Whichever one lets them sneer hardest.

I tried explaining RPN to them a year ago. They still insist there's parentheses in it. Today they called it an "app."

Dogmatic patience vampire is still trying to bait me into further wasted effort.

[–] JackbyDev@programming.dev 2 points 1 week ago (1 children)

Wowww. Insisting that they're good at math. I distinctly remember learning that RPN doesn't need parentheses in college.

reverse Polish calculators do not need expressions to be parenthesized

https://en.wikipedia.org/wiki/Reverse_Polish_notation

But, you know, anyone can edit Wikipedia. Someone probably put that there who hasn't opened a math textbook.

[–] mindbleach@sh.itjust.works 2 points 1 week ago

Oh of course. The sky isn't blue unless that's written in a maths textbook.

And if you look up and see stars, it's still blue, because it's written in a maths textbook! Are you saying a teacher could be wrong?!, smug emoji, crying emoji, roll-eyes emoji?

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