• Truscape@lemmy.blahaj.zone
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    3 months ago

    Presuming PEMDAS is our order of operations and the 5 next to the parentheses indicates multiplication…

    2+5(8-5) -> 2+5(3) -> 2+15=17

    Other than adding a multiplication indicator next to the left parentheses for clarification (I believe it’s * for programming and text chat purposes, a miniature “x” or dot for pen and paper/traditional calculators), this seems fine, yeah.

    …I worry about how many people may not understand how to solve equations like these.

    • DarkCloud@lemmy.world
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      3 months ago

      I prefer BM-DAS, no one’s out here doing exponents, and no one calls brackets “parentheses”…

      • cobysev@lemmy.world
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        3 months ago

        The way I was taught growing up, brackets are [these]. Parenthesis are (these).

        Yes, technically the latter are also brackets. But they can also be called parenthesis, whereas the former is exclusively a bracket. So we were taught to call them separate words to differentiate while doing equations.

        • DarkCloud@lemmy.world
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          Yeah, but as an adult it depends entirely on whether you’re in an industry or hobby that requires that level of bracket nuance/exponents.

          Most of us are just trying to remember the basics.

        • Droggelbecher@lemmy.world
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          3 months ago

          I’m a theoretical physics grad student and a night school maths teacher, I have never heard this distinction. People in academia around me call them round and square brackets.

          • tigeruppercut@lemmy.zip
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            3 months ago

            It’s a US vs UK (and probably others) distinction. The ( ) are almost never called brackets in the US, unless it’s a regional thing I’m not aware of. Also the [ ] didn’t get used in any math classes I was in the US up through calculus except for matrices.

            • Droggelbecher@lemmy.world
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              3 months ago

              Interesting! Nobody at my institute is a native English speaker. They’re from several European and some Asian and south American countries.

      • Deebster@infosec.pub
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        3 months ago

        I learnt it as BODMAS (brackets, orders, division and multiplication, addition and subtraction).

        Edit: I see we’re repeating points from the earlier posts down there 👇 (with default sort).

    • Alaknár@sopuli.xyz
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      3 months ago

      Multiplication sign is not required in situations like this. Same with unknowns - you don’t have to write 2*x, you just write 2x.

    • TheRedSpade@lemmy.world
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      While I never failed a math class, I also never went past high school. When would your presumptions NOT be true?

      • Truscape@lemmy.blahaj.zone
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        3 months ago

        Some forms of programming syntax, although there are the fringe cases where an equation (or function in programming) is represented by a symbol in conjunction with a parentheses input.

        For example:

        y(x) = 2*x+3

        5+y(1) = 10, as 1 is substituted in for x in the prior equation.

  • Saapas@piefed.zip
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    3 months ago

    Something funny about everyone being so eager to show how they can solve this

    • Dekkia@this.doesnotcut.it
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      3 months ago

      Counterpoint:

      If kids where taught how to solve them properly we wouldn’t need to dumb down equasions.

    • prole@lemmy.blahaj.zone
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      3 months ago

      What? A number next to parenthesis always means multiplication. Are people really not taught this anymore?

      • x4740N@lemmy.world
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        I live in Australia and don’t recall my school at all teaching me this in maths class

        They taught us stuff like radius and area of a circle but not this

        Edit:

        Also counterpoint, people exist that live in other countries and every countries education system is different

        • I live in Australia and don’t recall my school at all teaching me this in maths class

          I’m in Australia, and I remember being taught it, and I teach it.

          people exist that live in other countries and every countries education system is different

          The rules are the same everywhere, only the notation varies (in Germany they use . for multiply and : for divide, and say “dot before slash”, slash being - and +).

        • prole@lemmy.blahaj.zone
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          3 months ago

          I thought math was relatively universal. The US education system may be different, but I’m certain we’re not the only place that does it that way.

          • I thought math was relatively universal

            It is

            The US education system may be different

            They have the same rules, but they don’t require Maths teachers to have a Maths qualification (in Australia you have to have a Masters), and they have been sliding in world rankings for more than a decade.

    • Natanox@discuss.tchncs.de
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      3 months ago

      Why should anyone do that, an implied multiplication is the normal thing you learn in (I think?) somewhere between 5th to 7th grade. You only add an operator if it’s something else. It’s as basic as PEMDAS.

      • an implied multiplication

        There’s no such thing. It’s a Term/Product.

        is the normal thing you learn in (I think?) somewhere between 5th to 7th grade

        Yes, you learn that it’s a Term/Product in Year 7

        You only add an operator if it’s something else

        You never add an operator, or you end up with wrong answers.

        • Natanox@discuss.tchncs.de
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          3 months ago

          Aaah, got it. So if I see something like “5-(2+4)” I will just remove the subtraction operator and call it a day. Smartman on the internet said so. 🥴

          Also casual reminder not everyone on the internet is a native english speaker. Everyone but you knew what was meant.

          • So if I see something like “5-(2+4)” I will just remove the subtraction operator and call it a day

            Nope. Never said anything of the sort.

            Smartman on the internet said so

            No I didn’t, but nice try at a strawman 😂

            not everyone on the internet is a native english speaker. Everyone but you knew what was meant.

            There is no such thing as “implied multiplication” in any language. They are called Terms/Products in whatever language that book is using.

    • kameecoding@lemmy.world
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      3 months ago

      Google implied multiplication.

      Do you write 2x or do you write 2 • x?

      That’s implied multiplication, if x= (a+b) then 2x becomes 2(a+b). Implied multiplication

      • 💡𝚂𝗆𝖺𝗋𝗍𝗆𝖺𝗇 𝙰𝗉𝗉𝗌📱@programming.dev
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        3 months ago

        Google implied multiplication

        There’s no such thing. It’s a Term/Product. Google is a prime source of Maths disinformation (yes, they have been told it’s wrong, repeatedly, so it’s disinformation).

        Do you write 2x or do you write 2 • x?

        2a=(2xa) by definition, and 5(8-5)=(5x8-5x5).

        That’s implied multiplication

        No, that’s a Term/Product.

        Implied multiplication

        Terms/Products

  • jjjalljs@ttrpg.network
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    3 months ago

    I got some people really angry at me when I suggested writing some math expression with parenthesis so it would be clearer. I think someone told me that order of operations is like a natural law and not a convention, and thus everyone should know it or be able to figure it out.

    • stray@pawb.social
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      3 months ago

      I sometimes like to add unnecessary parentheses or brackets to section things off and improve legibility, but I don’t do any math stuff collaboratively, so I have no idea whether others would find that disruptive or helpful.

      • Feathercrown@lemmy.world
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        I do this, sometimes it helps reveal a natural pattern when some parts of earlier terms have “disappeared” to simplification

    • Alaknár@sopuli.xyz
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      I mean, there are very few ambiguous cases when you know how the order of operations works.

    • merc@sh.itjust.works
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      I got really angry because the prettier code formatter insists on removing parentheses, making things less clear. Because it’s an “opinionated” formatter you can’t tell it not to do that without using ugly hacks.

      Sure, logically there are times when you don’t need them. But, often it helps to explain what’s happening in the code when you can use parentheses to group certain things. It helps in particular when you want to use “&&” and “||” to say “do X only if Y fails”.

    • 💡𝚂𝗆𝖺𝗋𝗍𝗆𝖺𝗇 𝙰𝗉𝗉𝗌📱@programming.dev
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      so it would be clearer

      That’s because it’s already clear as is, as per the rules of Maths.

      I think someone told me that order of operations is like a natural law

      It’s a natural consequence of the definitions of the operators. e.g. Multiplication is shorthand for repeated Addition - 2x3=2+2+2 - so if you don’t do it before addition you end up with wrong answers. The order of operations rules is in fact just breaking everything down into Addition and Subtraction and then solving from there.

      not a convention

      There are some conventions, like left to right, but in that case that’s only because students tend to make mistakes with signs when they don’t go from left to right, so it’s there to preserve teachers sanity.

      • jjjalljs@ttrpg.network
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        3 months ago

        That’s because it’s already clear as is, as per the rules of Maths.

        More people evaluate 2+3x4 incorrectly than 2+(3x4). So, no, your answer does not hold up to my observed reality. You can throw as many “well technically” and “well actually” as you want, but that’s not going to fix the bug or make a pr.

        • More people evaluate 2+3x4 incorrectly than 2+(3x4)

          The people who have forgotten the rules of Maths, and the mnemonics even! 😂

          So, no, your answer does not hold up to my observed reality

          So try observing a real Maths textbook then. Students have no trouble at all with this, only adults who’ve forgotten the rules.

          • jjjalljs@ttrpg.network
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            Adults who have forgotten the rules who I work with and read/write code where it’s important. In the real world.

            This is like some pure maths vs real life engineering cliché.

            You’re either being deliberately obtuse or you’re painfully naive.

            • Adults who have forgotten the rules who I work with and read/write code where it’s important

              And as a consequence of that, MathGPT is the only e-calc which gives correct answers to order of operations! 😂

              This is like some pure maths vs real life engineering cliché

              It’s a Correct Maths vs. Programmers who have forgotten the rules cliche

              You’re either being deliberately obtuse or you’re painfully naive

              Neither, I’m a Maths teacher

              • jjjalljs@ttrpg.network
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                3 months ago

                I like and respect teachers, but I’m a software developer and I’m telling you that adding extra parenthesis often adds clarity and makes the whole process smoother. You exist in a whole other context that has norms and assumptions that do not apply to what I’m talking about.

                You being technically correct is irrelevant.

                • I’m a software developer

                  So am I

                  adding extra parenthesis often adds clarity

                  Everyone I’ve seen add Brackets to it has done so in the WRONG place and given WRONG answers. Again this is an issue of programmers not checking the rules of Maths

                  that do not apply to what I’m talking about

                  The rules of Maths always apply to all Maths

  • SSUPII@sopuli.xyz
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    3 months ago

    I feel like I am getting trolled

    Isn’t 17 the actual right answer?

      • SSUPII@sopuli.xyz
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        Yeah I know that. But I was feeling confused as to why it was here. That’s why I was feeling trolled, because it made me doubt basic math for being posted in a memes community.

        • JackbyDev@programming.dev
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          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.

            • MotoAsh@piefed.social
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              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
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              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

              • The P in PEMDAS means to solve everything within parentheses first

                and without a(b+c)=(ab+ac), now solve (ab+ac)

                there is no “distribution” step or rule

                It’s a LAW of Maths actually, The Distributive Law.

                that says multiplying without a visible operator

                It’s not “Multiplying”, it’s Distributing, a(b+c)=(ab+ac)

                So yes, 36 is valid here

                No it isn’t. To get 36 you have disobeyed The Distributive Law, thus it is a wrong answer

                It’s mostly because

                people like you try to gaslight others that there’s no such thing as The Distributive Law

                • Feathercrown@lemmy.world
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                  Are you under the impression that atomizing your opponents statements and making a comment about each part individually without addressing the actual point (how those facts fit together) is a good debate tactic? Because it seems like all you’ve done is confuse yourself about what I was saying and make arguments that don’t address it. Never mind that some of those micro-rebuttals aren’t even correct.

            • JackbyDev@programming.dev
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              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.

              • 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
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                  3 months ago

                  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]

          • lad@programming.dev
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            3 months ago

            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

        • NewDark@lemmings.world
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          I think it’s meant to play with your expectations. Normally someone’s take being posted is to show them being confidently stupid, otherwise it isn’t as interesting and doesn’t go viral.However, because we’re primed to view it from that lens, we feel crazy to think we’re doing the math correctly and getting the “wrong answer” from what we assume is the “confident dipshit”.

          There’s layers beyond the superficial.

          • namingthingsiseasy@programming.dev
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            I fell for it. It’s crazy to think how heavily I’ve been trained to believe everything I see is wrong in the most embarrassing and laughable way possible. That’s pretty depressing if you think about it.

        • 0x0@lemmy.zip
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          More like a sad realization of the state of (un)education in some parts of the so-called civilized world.
          You laugh not to cry.

    • marcos@lemmy.world
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      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
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        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

        • I mean, arithmetic order is just convention

          Nope, rules arising from the definition of the operators in the first place.

          not a mathematical truth

          It most certainly is a mathematical truth!

          But that convention works in the way we know, yes, because that’s what’s… well… convention

          The mnemonics are conventions, the rules are rules

          • SkyeStarfall@lemmy.blahaj.zone
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            The rules are socially agreed upon. They are not a mathematical truth. There is nothing about the order of multiple different operators in the definition of the operators themselves. An operator is simply just a function or mapping, and you can order those however you like. All that matters is just what calculation it is that you’re after

            • The rules are socially agreed upon

              Nope! Universal laws.

              They are not a mathematical truth.

              Yes they are! 😂

              There is nothing about the order of multiple different operators in the definition of the operators themselves

              That’s exactly where it is. 2x3 is defined as 2+2+2, therefore if you don’t do Multiplication before Addition you get wrong answers

              you can order those however you like.

              No you can’t! 😂 2+3x4=5x4=20, Oops! WRONG ANSWER 😂

              All that matters is just what calculation it is that you’re after

              And if you want the right answer then you have to obey the order of operations rules

              • SkyeStarfall@lemmy.blahaj.zone
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                That’s a very simplistic view of maths. It’s convention https://en.wikipedia.org/wiki/Order_of_operations

                Just because a definition of an operator contains another operator, does not require that operator to take precedence. As you pointed out, 2+3*4 could just as well be calculated to 5*4 and thus 20. There’s no mathematical contradiction there. Nothing broke. You just get a different answer. This is all perfectly in line with how maths work.

                You can think of operators as functions, in that case, you could rewrite 2+3*4 as add(2, mult(3, 4)), for typical convention. But it could just as well be mult(add(2, 3), 4), where addition takes precedence. Or, similarly, for 2*3+4, as add(mult(2, 3), 4) for typical convention, or mult(2, add(3, 4)), where addition takes precedence. And I hope you see how, in here, everything seems to work just fine, it just depends on how you rearrange things. This sort of functional breakdown of operators is much closer to mathematical reality, and our operators is just convention, to make it easier to read.

                Something in between would be requiring parentheses around every operator, to enforce order. Such as (2+(3*4)) or ((2+3)*4)

                • That’s a very simplistic view of maths

                  The Distributive Law and Arithmetic is very simple.

                  It’s convention

                  Nope, a literal Law. See screenshot

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

                  Isn’t a Maths textbook, and has many mistakes in it

                  Just because a definition of an operator contains another operator, does not require that operator to take precedence

                  Yes it does 😂

                  2+3x4=2+3+3+3+3=14 by definition of Multiplication

                  2+3x4=5x4=20 Oops! WRONG ANSWER 😂

                  As you pointed out, 2+34 could just as well be calculated to 54 and thus 20

                  No, I pointed out that it can’t be calculated like that, you get a wrong answer, and you get a wrong answer because 3x4=3+3+3+3 by definition

                  There’s no mathematical contradiction there

                  Just a wrong answer and a right one. If I have 1 2 litre bottle of milk, and 4 3 litre bottles of milk, even young kids know how to count up how many litres I have. Go ahead and ask them what the correct answer is 🙄

                  Nothing broke

                  You got a wrong answer when you broke the rules of Maths. Spoiler alert: I don’t have 20 litres of milk

                  You just get a different answer

                  A provably wrong answer 😂

                  This is all perfectly in line with how maths work

                  2+3x4=20 is not in line with how Maths works. 2+3+3+3+3 does not equal 20 😂

                  add(2, mult(3, 4)), for typical

                  rule

                  But it could just as well be mult(add(2, 3), 4), where addition takes precedence

                  And it gives you a wrong answer 🙄 I still don’t have 20 litres of milk

                  And I hope you see how, in here, everything seems to work just fine

                  No, I see quite clearly that I have 14 litres of milk, not 20 litres of milk. Even a young kid can count up and tell you that

                  it just depends on how you rearrange things

                  Correctly or not

                  our operators is just convention

                  The notation is, the rules aren’t

                  Something in between would be requiring parentheses around every operator, to enforce order

                  No it wouldn’t. You know we’ve only been using brackets in Maths for 300 years, right? Order of operations is much older than that

                  Such as (2+(3*4))

                  Which is exactly how they did it before we started using Brackets in Maths 😂 2+3x4=2+3+3+3+3=14, not complicated.

        • marcos@lemmy.world
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          3 months 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.

          • Social conventions are real, well defined things

            So are the laws of nature, that Maths arises from

            Some mathematicians like to pretend they aren’t, while using a truckload of them; that’s a hypocritical opinion

            No, you making false accusations against Mathematicians is a strawman

            That’s not to say you can’t change them

            You can change the conventions, you cannot change the rules

            But all of basic arithmetic is a social convention

            Nope, law of nature. Even several animals know how to count.

            you can redefine the numbers and operations any time you want too

            And you end up back where you started, since you can’t change the laws of nature

      • Petter1@discuss.tchncs.de
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        Well, this is just a writing standard that is globally agreed on,

        The writing rules are defined by humans not by natural force
        (That one thing and another thing are two things, is a rule from nature, as comparison)

        • this is just a writing standard that is globally agreed on

          No, it’s a universal rule of Maths

          The writing rules are defined by humans not by natural force

          Maths is for describing natural forces, and is subject to those laws

          That one thing and another thing are two things, is a rule from nature

          Yep, there are even some animals who understand that, and all of Maths is based upon it.

        • mindbleach@sh.itjust.works
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          3 months ago

          Save yourself the trouble - Smartman Apps is a crank. They categorically will not comprehend the difference between the notation we made up and how numbers work. Dingus keeps saying ‘animals can count’ like that proves parentheses-first is completely different! from distribution.

          Why’d Russel and Whitehead bother with the Principia Mathematica when they could just point to Clever Hans?

      • Some people insist there’s no “correct” order for the basic arithmetic operations.

        And those people are wrong

        And worse, some people insist the correct order is parenthesis first, then left to right

        As per Maths textbooks

        Both of those sets of people are wrong

        All Maths textbooks are wrong?? 😂

      • MotoAsh@piefed.social
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        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.

            • Feathercrown@lemmy.world
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              3 months ago

              They do, it’s grouping those operations to say that they have the same precedence. Without them it implies you always do addition before subtraction, for example.

              • 💡𝚂𝗆𝖺𝗋𝗍𝗆𝖺𝗇 𝙰𝗉𝗉𝗌📱@programming.dev
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                3 months ago

                They do, it’s grouping those operations to say that they have the same precedence

                They don’t. It’s irrelevant that they have the same priority. MD and DM are both correct, and AS and SA are both correct. 2+3-1=4 is correct, -1+3+2=4 is correct.

                Without them it implies you always do addition before subtraction, for example

                And there’s absolutely nothing wrong with doing that, for example. You still always get the correct answer 🙄

                • Feathercrown@lemmy.world
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                  Uh, no. I don’t think you’ve thought this through, or you’re just using (AS) without realizing it. Conversations around operator precedence can cause real differences in how expressions are evaluated and if you think everyone else is just being pedantic or is confused then you might not underatand it yourself.

                  Take for example the expression 3-2+1.

                  With (AS), 3-2+1 = (3-2)+1 = 1+1 = 2. This is what you would expect, since we do generally agree to evaluate addition and subtraction with the same precedence left-to-right.

                  With SA, the evaluation is the same, and you get the same answer. No issue there for this expression.

                  But with AS, 3-2+1 = 3-(2+1) = 3-3 = 0. So evaluating addition with higher precedence rather than equal precedence yields a different answer.

                  =====

                  Some other pedantic notes you may find interesting:

                  There is no “correct answer” to an expression without defining the order of operations on that expression. Addition, subtraction, etc. are mathematical necessities that must work the way they do. But PE(MD)(AS) is something we made up; there is no actual reason why that must be the operator precedence rule we use, and this is what causes issues with communicating about these things. People don’t realize that writing mathematical expressions out using operator symbols and applying PE(MD)(AS) to evaluate that expression is a choice, an arbitrary decision we made, rather than something fundamental like most everything else they were taught in math class. See also Reverse Polish Notation.

                  Your second example, -1+3+2=4, actually opens up an interesting can of worms. Is negation a different operation than subtraction? You can define it that way. Some people do this, with a smaller, slightly higher subtraction sign before a number indicating negation. Formal definitions sometimes do this too, because operators typically have a set number of arguments, so subtraction is a-b and negation is -c. This avoids issues with expressions starting with a negative number being technically invalid for a two-argument definition of subtraction. Alternatively, you can also define -1 as a single symbol that indicates negative one, not as a negation operation followed by a positive one. These distinctions are for the most part pedantic formalities, but without them you could argue that -1+3+2 evaluated with addition having a higher precedence than subtraction is -(1+3+2) = -6. Defining negation as a separate operation with higher precedence than addition or subtraction, or just saying it’s subtraction and all subtraction has higher prexedence than addition, or saying that -1 is a single symbol, all instead give you your expected answer of 4. Isn’t that interesting?

        • orbitz@lemmy.ca
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          3 months 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.

        • DefederateLemmyMl@feddit.nl
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          3 months ago

          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

          • MotoAsh@piefed.social
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            3 months ago

            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.

              • MotoAsh@piefed.social
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                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”.

          • KubeRoot@discuss.tchncs.de
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            3 months ago

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

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

              • KubeRoot@discuss.tchncs.de
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                3 months ago

                I did not flip any signs, merely reversed the order in which the operations are written out. If you read the right side from right to left, it has the same meaning as the left side from left to right.

                Hell, the convention that the sign is on the left is also just a convention, as is the idea that the smallest digit is on the right (which should be a familiar issue to programmers, if you look up big endian vs little endian)

                • I did not flip any signs

                  Yes you did! 😂

                  merely reversed the order in which the operations are written out

                  No, merely reversing the order gives -3-2+1 - you changed the signs on the 1 and 3.

                  If you read the right side from right to left, it

                  Starts with -3, which you changed to +3

                  it has the same meaning as the left side from left to right

                  when you don’t change any of the signs it does 😂

                  Hell, the convention that the sign is on the left is also just a convention

                  Nope, it’s a rule of Maths, Left Associativity.

                • howrar@lemmy.ca
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                  3 months ago

                  If that’s your idea of reversing the order, then you’re not talking about the same thing as SpaceCadet@feddit.nl. They’re talking about the order of operations and the associativity/commutativity property. You’re talking about the order of the symbols.

  • Triasha@lemmy.world
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    3 months ago

    Pemdas, parenthesis first, for a total of 3. Then multiplication, 15, then addition. 17. What’s hard about this?

  • Sertou@lemmy.world
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    Or it simply could be that I haven’t needed to concern myself with the order of operations more than a dozen times since high school. Even when working as a web coder it was so seldom necessary that I can’t recall a single example.

    The US education system was still pretty decent when I was in middle and high school in the 1980s, so we definitely covered this in algebra.