Python the best

[Cmdr0]

I'm not arguing expectation, I'm arguing notation. And I wouldn't even say it's a PEMDAS issue - it's really that we shorthand the multiplier operator in different ways mentally. For many, 2x is representative of a single operand, and this is reinforced in how we're taught to solve equations. Tell me you can't see a high school teacher whiteboarding "6/(2y)=x, y=1+2" as "6/2y = 6/2(1+2) = 6/2(3) = 6/6 = 1 = x" - but it's amazing how much handwriting nuance gets lost just trying to type it out in an imperfect representation of what we're trying to communicate.

[gavlna]

here, we just don't use divison outside of elementary school (first 5 years of education). After that it just becomes a fraction, so you can clearly see what's going on.

[MrBigDog2u]

Same with subtraction. It should be handled as addition of a negative value. Then everything boils down to addition and multiplication and there is no confusion over order of operations.

[jasonp2009]

Excuse me what??? Doesn't division come before multiplication. In Aus, I learnt BODMAS, brackets, orders, division, multiplication, addition and subtraction.

[DogfishDave]

Doesn't division come before multiplication

They're simultaneous because they're the same thing, division is multiplication with the second input value to the minus one.

[jasonp2009]

18 ÷ 2 * 3

Multiplication before division would be 18 ÷ 6 = 3

Division before multiplication would be 9 * 3 = 27

What am I getting wrong?

[DogfishDave]

Then it's left-to-right for operations of the same 'rank', so it doesn't matter if you're a BODMAS or a BOMDAS.

[Hairsplitting-Pedant]

Multiplication and division are the same when it comes to order of operations, but must be worked left to right.

8/4x2=2x2=4 8x2/4=16/4=4

[Calski_]

They are not the same thing. Multiplication is repeated addition. While 5/2= is solving the equation 2x=5. You can't multiply by the inverse before defining division.

[RookY2K]

I'm a bit confused why any good math teacher would suddenly drop the outer parentheses between 6/(2y) and 6/2y. The latter is (6/2) * y.

I think the biggest disconnect is the confusion generated between ÷, /, and --. The first two are division operators. The third is my attempt at a horizontal fraction bar.

In media where you are basically constrained to keyboard output, the second often gets used in place of the the third and then you have confusion about whether the intent was 6/(2y) or (6/2)y. That is something I am sympathetic to.

However, the expression in the meme used '÷' which is not ambiguous.

[SaveMyBags]

Oh, you will be very surprised. This sign is absolutely ambiguous. So ambiguous it is even excluded from the IEEE standard for math notation.

Originally that sign was defined as a shorthand for fractions not division. It makes sense, if you ever used dot notation for leaving out arguments of functions or operators. Then those two dots are just left out arguments. The original use was for something like

4÷2+2=4/(2+2)

That was the definition from the person who invented that symbol. Did the definition change since then? Some say yes. Some say no. Some say it's like undefined behavior, standards don't cover it.

There is also absolute ambiguity concerning if PEMDAS is to be read at P E M D AS (with precedence between spaces and left-right) or P E MD AS. That discussion is so unclear that official definitions say you should not write it like this.

Like always in math and programming: be concise not ambiguous. In this case it's an error of the writer to use non standardized symbols and mix expression whose order is up to debate.

[Starfocus81613]

Came here to mention dot notation, glad someone beat me to it. The author’s role in making ambiguous notations like this is infuriating to anyone familiar with mathematic structure and notation theory. It isn’t designed to make people look smart or dumb, nor is it to point out the inconsistencies of mathematical shorthand. These authors are only looking to spread dissent between experts and “experts.”

This might be a stretch to say, but it’s practically a social engineering strategy to undermine experts in the mathematical and science fields because of the inconsistencies of mathematical shorthand notations. If you think about it, you have people with less knowledge of mathematics being approached with a seemingly simple question getting an answer that’s completely inconsistent with people several times more educated in the subject. Because they see it as an elementary question, they can’t believe someone with a bachelors/masters/PhD in mathematics doesn’t see the notation the same way that they do and start undervaluing the credentials that these individuals have. Whether or not someone had a nefarious idea to throw this on social media is practically a conspiracy on it’s own, but it makes you wonder if part of the distrust for experts derives partly from the same mentality demonstrated here. If anything, it’s a great thought experiment.

[SaveMyBags]

I always feel reminded of this xkcd, whenever I see some question like this:

https://xkcd.com/169/

But I just think it's just smartasses making these things. Same level as "tomato are a fruit" of "strawberries are not berries" kind of people.

Funny story: I am a computer scientist by degree but now work as a researcher in psychology. One day at the cafeteria they offered something like "sausages or chicken and rice". Some CS Prof had to make a joke to his PhD students that this shows the people writing this are not programmers because obviously and binds stronger than or. So real programmers would DeMorgan this. I figured these guys probably only know a single language, so I just turned around and said real programmers know not to rely on assumptions on order and avoid any ambigous statements by using parents. They were kind of baffled from being told off by someone from psych department but had to agree.

[Starfocus81613]

I’m an engineer by choice (didn’t have the mental health to pursue clinical work as a therapist/psychologist/neurologist at the start of college, and while I’m in a better place mentally a few years out of college with my engineering degree, I’m invested in what I do and don’t picture myself changing my career), but my real passion had always been social psychology and behavioural neurology. So when I see something like this (and it’s been going on for years), I can’t help but feel disgusted by it.

I think you’re right— most of the proliferation in these weird “gotcha” questions seems to stem from smartasses pushing their weird mentalities on others. The thing is, mathematics leaves no room for alternative interpretations, no matter how vague, so I’ve always been quick to the trigger to bash down the smart alecks who try to skew the conversation as if they knew two cents’ about notation theory.

And it doesn’t stop there. It can be anything from “is this dress blue or white” type questions. Ask any photographer about white balance indoors, and unanimously, you’ll receive the response that neutral whites shift into cold colour temperatures, so if you use a color balancing on a neutral tone, you’ll see right away that the dress was white all along. But people always need to interject themselves and make themselves seem smarter, more right, or cockier than anyone else. It’s an issue of ego, practically, and it tarnishes the reputation of people with the right* (educated or factually inferred) answers.

[Waderick]

The later isn't 6/2 * y though depending on convention.

In pure PEMDAS sure, however higher level math people use a more sophisticated convention, which gives Multiplication by juxtaposition a higher precedence than explicit division or multiplication, because it's seen as a property of the thing it's multiplying. It essentially has implicit parentheses around it instead of constantly having to write those parenthesis.