• kryptonianCodeMonkey@lemmy.world
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          11 months ago

          That’s wrong. Multiplication and division have equal precedence, same as addition and subtraction. You do them left to right. PEMDAS could be rewritten like PE(MD)(AS). After parentheses and exponents, it"s Multiplication and division together, then addition and subtraction together. They also teach BODMAS some places, which is “brackets, order, division and multiplication, addition and subtraction” Despite reversing the division and multiplication, it doesn’t change the order of operations. They have the same priority, so they are just done left to right. PEMDAS and BODMAS are the different shorthand for the same order of operations.

          • starman2112@sh.itjust.works
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            11 months ago

            They were right but for the wrong reason. Implied multiplication–that is, a(b) or ab–often comes before explicit multiplication and division. Apparently it’s up to the person writing the equation, so the meme is intentionally and explicitly ambiguous

            • kryptonianCodeMonkey@lemmy.world
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              11 months ago

              They’re still wrong, in my humble opinion. I’m aware of this notion, and I’ve even had people share a snip from some book that states this as fact. However, this is not standardized and without the convention being widely understood and recognized as the standard in the world of mathematics (which generally doesn’t use the symbol (÷) at all at post-algebra levels), there is no reason to treat it as such just because a few people assert it is should be.

              It doesn’t make sense at all to me that implied multiplication would be treated any differently, let alone at a higher priority, than explicit multiplication. They’re both the same operation, just with different notations, the former of which we use as shorthand.

              There are obviously examples that show the use of the division symbol without parentheses sometimes leads to misunderstandings like this. It’s why that symbol is not used by real mathematicians at all. It is just abundantly more clear what you’re saying if you use the fraction bar notation (the line with numerator on top and denominator on bottom). But the rules as actually written, when followed, only reach one conclusion for this problem and others like it. x÷y(z) is the SAME as x÷y*z. There’s no mathematical or logical reason to treat it differently. If you meant for the implicit multiplication to have priority it should be in parentheses, x÷(y(z)), or written with the fraction bar notation.

              • Tlaloc_Temporal@lemmy.ca
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                11 months ago

                Implicit multiplication being before regular multiplication/division is so we can write 2y/3x instead of (2y)/(3x). Without priority, 2y/3x becomes (2y÷3)•x.

                Coefficients are widely used enough that mathematicians don’t want to write parentheses around every single one. So implicit multiplication gets priority.

                • kryptonianCodeMonkey@lemmy.world
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                  11 months ago

                  I think one could argue a coefficient on an unknown variable, like 2y, should take higher priority simply because it cannot be any further resolved or simplified. That is not the case with, say, 2(3+1). Although that does still leave you with potential ambiguity with division/multiplication, such has 1/7y. Is the coefficient 7, or is it 1/7? i.e. Is that 1/(7y)? Or (1/7)y? Either way, if that’s not the the standard understood by everyone, then it is a non-standard, inconsistent rule. And as demonstrated, if you do use that rule, it needs to be more clearly defined. That is the source of this “ambiguity”. If you don’t include it, the order of operations rules, as written, are clear.

                  • 2y, should take higher priority simply because it cannot be any further resolved or simplified

                    Bingo!

                    That is not the case with, say, 2(3+1)

                    It’s the same thing, where y=3+1.

                    1/7y. Is the coefficient 7, or is it 1/7? i.e. Is that 1/(7y)

                    Yes, it’s 1/(7y) as per the definition of Terms.

                    Either way, if that’s not the the standard understood by everyone

                    It’s the standard in literally every Maths textbook.

                  • Tlaloc_Temporal@lemmy.ca
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                    11 months ago

                    I agree it needs to be more clearly defined, but one of the reasons it wasn’t clearly defined was because mathematicians thought it was so universal it didn’t need defining, like how parentheses work to begin with.

                    Casio tried not doing umplicit multiplication after some american teachers complained, then went back to doing it after everyone else complained. Implicit multiplication is the standard.

              • I’ve even had people share a snip from some book that states this as fact

                A Maths textbook.

                However, this is not standardized

                It’s standard in every Maths textbook.

                there is no reason to treat it as such just because a few people assert it is should be

                The “few people” are Maths teachers and Maths textbook authors.

                It doesn’t make sense at all to me that implied multiplication would be treated any differently

                There’s no such thing as implicit multiplication

                They’re both the same operation

                No, what people are calling “implicit multiplication” is either The Distributive Law - which is the first step in solving Brackets - or Terms - and neither of these things is “multiplication”. Multiplication literally refers to multiplication symbols only.

                It’s why that symbol is not used by real mathematicians at all. It is just abundantly more clear what you’re saying if you use the fraction bar notation

                The division symbol is used - it is not the same thing as a fraction bar.

                x÷y(z) is the SAME as x÷y*z.

                No, it’s the same as x÷(y*z).

                There’s no mathematical or logical reason to treat it differently

                Terms, The Distributive Law, are why it’s treated differently.

        • 0ops@lemm.ee
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          11 months ago

          There’s an argument to be made that implicit multiplication comes before division, resulting in the answer 1, but all multiplication? That’s wrong, full-stop. You calculate (explicit) multiplication and division in one step, left to right. Reason being that division is technically just multiplying by the reciprocal.

      • Zagorath@aussie.zone
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        11 months ago

        No, because implicit multiplication binds more tightly than explicit. a/b© becomes a/(bש)

          • Zagorath@aussie.zone
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            11 months ago

            Most maths textbooks written by mathematicians.

            I don’t mean when they’re explaining “here’s how the order of operations works”. I mean in the basic way that they write more advanced problems and the answers they give for them.

            This video, and the prequel to it linked in the description, go into some detail showing who uses what convention and why.

            • Nihilore@lemmy.world
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              11 months ago

              Interestingly I’ve wondered if this is regional, as a fellow Aussie I learned the same as you but it seems in other places they learn the other way

              • Zagorath@aussie.zone
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                11 months ago

                FWIW I went to school in Asia, using an internationally-focused curriculum, rather than going through the Australian curriculum here in Aus.

                The video I linked includes some discussion with a calculator manufacturer who apparently is under the impression that teachers in North America are asking for strict BIDMAS, so the calculator manufacturer actually switched their calculators to doing that. Until they then got blowback from the rest of the world’s teachers, so they switched back to BIDMAS with juxtaposition being prioritised over division. The video also presents the case that outside of teachers—among actual maths and physics academics—prioritising juxtaposition is always preferred, even in North America.

              • I’m an Australian teacher who has also taught the U.K. curriculum (so I have textbooks from both countries) and, based on these comments you mention, have also Googled some U.S. textbooks, and I’ve yet to see any Maths textbooks that teach it “the other way”. I have a very strong suspicion that it’s just a lot of people in the U.S. claiming they were taught that way, but not actually being true. I had someone from Europe claim the way we (and the U.K.) teach it wasn’t taught there (from memory it was Lithuania, but I’m not sure now), so I just Googled the curriculum for their country and found that indeed it is taught the same way there as here. i.e. people will just make up things in order not to admit they were wrong about something (or that their memory of it is faulty).

        • 0ops@lemm.ee
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          11 months ago

          That’s exactly where the calculators in the op differ. For more examples, Casio calculators do implicit multiplication first, while ti’s treat it the same as explicit multiplication and division. I think that the latter is more predictable personally, but really you just need to know your calculator.