I always thought maths, at least basic maths, was fairly black and white. 2 + 2 = 4. The only possible solution is 4. Any other answer is wrong.

Turns out, in your own country basic maths is black and white, but when you start leaping international borders it is suddenly… grey.

I grew up following the BODMAS rule. Turns out, in the US they follow the PEMDAS rule:

  • PEMDAS would see you work out what was inside the brackets first and then multiply before dividing last, followed by addition then subtraction.
  • But the BODMAS method means you would solve the question this way instead: brackets, orders, division, multiplication, addition, subtraction.

Take the above sum. If I was to solve this in Australia using BODMAS you would solve brackets first (4), then divide 8 by 2 (also 4) then multiply 4 x 4 = 16.

Following the US method of PEMDAS you solve the brackets first (4), then multiply (2 x 4 = 8), then divide 8 by 8 = 1.

This means depending where you are in the world, the answer to the above equation is either 16 or 1. Is it just me, or does that seem to be a major problem?

I’m hoping some of my US readers can either confirm or deny the PEMDAS rule. And if it is correct, why are the rules different? Please explain so my head can stop hurting.

28 comments on “PEMDAS v BODMAS

  1. Giggling Fattie

    July 21, 2021 at 9:21 pm

    Okies so I have no idea how this would change the answer? And no, I’m not going to figure it out, but here in Canada we do BEDMAS. Or I guess now its called PEDMAS (parenthesis instead of brackets? I really don’t know or care cos I don’t teach that high level math)

    • BEDMAS would be the same as BODMAS – the UK influence I guess, which is why Australia does BODMAS.

      And I guess you’ll never teach higher? 😉

      • Giggling Fattie

        July 22, 2021 at 9:39 am

        Yyyyeeessss for the colonies! We have it proper lol

        I’m licensed as a primary (k-3) and junior (4-6) but I am very much a primary person haha!

  2. No idea, Anita! Maths was my weakest subject!

  3. Well, I got 1 for my answer. Of course, I’m American. Let’s see what Google says…

    OMG–I think it’s 16! Besides Google, there’s a video with 2.6 million viewers that says 16

    I’m so confused.

    BTW, I got A’s in calculus! But not necessarily arithmetic.

    • Is your head hurting as well? It’s confusing isn’t it? Surely a math equation like that can only have one answer?!

      • I liked the video’s reason: that it’s an incomplete math sentence. Like “Throw momma from the train a kiss”. Not enough information to come up with a definitive answer.

        • I agree with that, but it really looks like a sum a teacher might give a class. It does look like it should be simple!

  4. It seems that the PEMDAS rule doesn’t specify multiplication first over division (or addition first over subtraction), but that the operations should be done left to right. (Which is how I’ve understood it.) So, yes, the above should be 16. I think the hang-up occurs when people decide that the parenthesis/brackets still matter after you’ve solved what’s inside them. Or they get really hung up on the acronym, which should really be PE–LeftToRight–MorDAorS. (I also never learned the acronym. *shrug*) In any case, such a math problem is like a badly written sentence: confusing and full of ambiguity.

    • Exactly, Katherine. With BODMAS we’ve always done left to right as well. When I was a kid we just learnt order of operations, we didn’t have an acronym, but the Barbarians have been taught it at school (they get a lot of acronyms).

  5. This is where parentheses come in handy: if you say 8/(2x(2+2)) it comes out right regardless.

  6. Giggling Fattie

    July 22, 2021 at 9:58 am

    Yeah! When I first interviewed for this job, it was for the junior classroom. But once they got their enrolment settled and assessed their needs it became a primary position which made it much easier for me to consider!

    • Definitely easier! Not long now for it all to begin. Looking forward to hearing all about it (good luck!).

  7. All those number based internet memes (that I constantly get wrong) suddenly make a whole lot more sense… It was never my math!

    • Haha, never your math, Nik. I think mathematician’s are secretly laughing at us – they’re probably the source of the memes so they can have a laugh.

  8. Parentheses = brackets. Then it’s multiplication/division. Then addition/subtraction. It’s pretty much left to right, but that usually doesn’t make a difference, at least with the problems they have the kiddos do when PEDMAS is the lesson. Multiplication and division are done at the same time as is addition and subtraction.

    (I don’t know what orders are. E stands for exponents.)

    That problem is written very ambiguously. Is it 8 divided by 2 or 8 divided by 2 x (2 + 2)? If it were on a test here, that would be explicitly stated.

    • Orders are equivalent to exponents. We say “to the order of 2” for example.

      If yours are left to right, then the equation is the same as ours, because our rule is left to right as well.

  9. The only difference is if your home country names a parentheses a bracket. The equation is still the same, they both run from left to right and have the same order.

    I was offered a half scholarship in math to the University of Miami in Coral Gables, but that was in 1974, I had to think about this one for a few minutes.

    P.S, 2+2 still equals 4

    • Did you take the half-scholarship? And you know what, BF, I reckon in this current world of crazy, if you told me 2+2 didn’t equal 4 anymore, I’d probably half believe you, lol 😉

      • No, I didn’t. My father passed when I was senior in high school. Since I only had a half day as a senior, because of advanced placement classes in my first two years, I took a couple of jabs to support Mom.

        I was a layout carpenter for Jim Walter Corp, now an international company, and I built those old bag in a box waterbeds.

        I went to USF, the local college, and graduated in three years. Took classes early in the day and then went to work. I was able to skip my first year of college, those 100 level classes used to thin the herd,

        • I’m so sorry to hear you lost your father at such a young age, BF. Your mum was very lucky to have you by the sounds. Doesn’t seem like you let anything stop you from forging ahead. That’s a huge credit to you.

  10. My best guess is that with PEMDAS (as with BODMAS) you perform the steps from left to right; so after solving parenthesis (4), the next step from the left is division (4), then multiplication 4 x 4 = 16.
    The tricky part is doing them in order from left to right.

    AJ, Michele gave an interesting answer to your question if you want to check it out:

    • I think you’re right, it’s the left to right bit that keeps it consistent. And I’ll check out Michele’s answer 🙂

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