• SSUPII@sopuli.xyz
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      18 days ago

      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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        17 days ago

        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.

          • JackbyDev@programming.dev
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            17 days ago

            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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                6 hours 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]

                • Please read this section of Wikipedia which talks about these topics better than I could

                  Please read Maths textbooks which explain it better than Joe Blow Your next Door neighbour on Wikipedia. there’s plenty in here

                  It shows that there is ambiguity in the order of operations

                  and is wrong about that, as proven by Maths textbooks

                  especially niche cases there is not a universally accepted order of operations when dealing with mixed division and multiplication

                  That’s because Multiplication and Division can be done in any order

                  It addresses everything you’ve mentioned

                  wrongly, as per Maths textbooks

                  Multiplication denoted by juxtaposition (also known as implied multiplication)

                  Nope. Terms/Products is what they are called. “implied multiplication” is a “rule” made up by people who have forgotten the actual rules.

                  s often given higher precedence than most other operations

                  Always is, because brackets first. ab=(axb) by definition

                  1 / 2n is interpreted to mean 1 / (2 · n)

                  As per the definition that ab=(axb), 1/2n=1/(2xn).

                  [2][10][14][15]

                  Did you look at the references, and note that there are no Maths textbooks listed?

                  the manuscript submission instructions for the Physical Review journals

                  Which isn’t a Maths textbook

                  the convention observed in physics textbooks

                  Also not Maths textbooks

                  mathematics textbooks such as Concrete Mathematics by Graham, Knuth, and Patashnik

                  Actually that is a Computer Science textbook, written for programmers. Knuth is a very famous programmer

                  More complicated cases are more ambiguous

                  None of them are ambiguous.

                  the notation 1 / 2π(a + b) could plausibly mean either 1 / [2π · (a + b)]

                  It does as per the rules of Maths, but more precisely it actually means 1 / (2πa + 2πb)

                  or [1 / (2π)] · (a + b).[18]

                  No, it can’t mean that unless it was written (1 / 2π)(a + b), which it wasn’t

                  Sometimes interpretation depends on context

                  Nope, never

                  more explicit expressions (a / b) / c or a / (b / c) are unambiguous

                  a/b/c is already unambiguous - left to right. 🙄

                  Image of two calculators getting different answers

                  With the exception of Texas Instruments, all the other calculator manufacturers have gone back to doing it correctly, and Sharp have always done it correctly.

                  6÷2(1+2) is interpreted as 6÷(2×(1+2))

                  6÷(2x1+2x2) actually, as per The Distributive Law, a(b+c)=(ab+ac)

                  (6÷2)×(1+2) by a TI-83 Plus calculator (lower)

                  Yep, Texas Instruments is the only one still doing it wrong

                  This ambiguity

                  doesn’t exist, as per Maths textbooks

                  “8 ÷ 2(2 + 2)”, for which there are two conflicting interpretations:

                  No there isn’t - you MUST obey The Distributive Law, a(b+c)=(ab+ac)

                  Mathematics education researcher Hung-Hsi Wu points out that “one never gets a computation of this type in real life”

                  And he was wrong about that. 🙄

                  calls such contrived examples

                  Which notably can be found in Maths textbooks

          • MotoAsh@piefed.social
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            17 days 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
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            17 days ago

            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

        • lad@programming.dev
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          17 days 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