[Vipvlad]

I'm actually a bit shocked at the lack of grasp on such simple math equations by most members here.

Since these things are used so little in the real world, people forget or couldn't be bothered to learn it in the first place, rather just copy it.

Basic maths is needed, but these sorts of equations are obnoxious.

[9mm_fan]

Since these things are used so little in the real world, people forget or couldn't be bothered to learn it in the first place, rather just copy it.

Basic maths is needed, but these sorts of equations are obnoxious.

I don't think it is obnoxious in the slightest but it's something that people should simply should know due to how basic it is.

I think equations like this are the equivalent to riding a bicycle. I never ride a bike anymore but I still remember how to do it.

[erubresen]

As far as I can remember, I was only taught PEMDAS, nothing about "left/right" etc. etc. I also vaguely remember that multiplication takes priority over division after doing what's in the parentheses.

However, I don't think I ever used order of operations after 6th or 7th grade. In upper maths the school told us to use the calculators, which were coincidentally TI-83s/TI-84s which give an answer of "2".

[MatueHarton]

As far as I can remember, I was only taught PEMDAS, nothing about "left/right" etc. etc. I also vaguely remember that multiplication takes priority over division after doing what's in the parentheses.

However, I don't think I ever used order of operations after 6th or 7th grade. In upper maths the school told us to use the calculators, which were coincidentally TI-83s/TI-84s which give an answer of "2".

Exactly. Some people in here can't grasp this. PEMDAS or BODMAS is what we were taught and nothing to do with left to right. Left to right sounds obvious, but I'd always be looking for something from the PEMDAS rule, so maybe doing multiplication before division.

I suppose this gives some people a moment to feel superior.

[Goodwin]

It's not about 'feeling superior' - it's about what's correct and what isn't. I wasn't taught BODMAS at school but nor was I taught about order of operations: I learnt the latter at university and the former through work. These days I spend a lot of time teaching them both to students but I emphasis the latter far more than the former, particularly since BODMAS can produce misunderstanding (such as always doing multiplication before division, regardless of how the expression is written).

Anyway, even if one wasn't explicitly taught the order of operations, it's intuitively correct for Western people given this is how text is written. Young students naturally work out a mathematical expression from left to right before they're introduced to BODMAS.

[erubresen]

Regardless, if this left/right thing is indeed correct, why in the world would it not be taught? Once PEMDAS is taught, left/right isn't intuitive at all (at least it isn't for me).

[EmxATW5m]

Then you weren't taught the Algebra Order of Operations, and if you weren't taught left-to-right you're in some serious trouble if you don't use it by common sense, even worse if you were taught multiplication over division.

Why? Let's use really simple example
4 / 5 * 6 / 3 * 5

Multiplication first?
4 / 5 * 6 / 3 * 5
= 4 / 30 / 3 * 5
= 4 / 30 / 15
= 0.1333333333333333 / 15
= 0.0088888888888889

Multiplication first, right to left?
4 / 5 * 6 / 3 * 5
= 4 / 5 * 6 / 3 / 15
= 4 / 30 / 3 / 15
= 4 / 30 / 0.2
= 3 / 150
= 0.02

Just right to left?
4 / 5 * 6 / 3 * 5
= 4 / 5 * 6 / 15
= 4 / 5 * 0.4
= 4 / 2
= 2


Correct way, left to right, multiplication and division are equal
4 / 5 * 6 / 3 * 5
= 0.8 * 6 / 3 * 5
= 4.8 / 3 * 5
= 1.6 * 5
= 8

You can ask anyone, 8 is the correct answer, multiplication first, or right to left, or both together both throw you far off from the correct answer.

edit:

Only reason I can figure out it's not taught (in western countries at least) is the fact that we normally read from left to right, too, so teachers might assume that it just comes out naturally.

[Vipvlad]

It's not about 'feeling superior' - it's about what's correct and what isn't. I wasn't taught BODMAS at school but nor was I taught about order of operations: I learnt the latter at university and the former through work. These days I spend a lot of time teaching them both to students but I emphasis the latter far more than the former, particularly since BODMAS can produce misunderstanding (such as always doing multiplication before division, regardless of how the expression is written).

This just proves Maths is a complete mess. Or at least the standards.

it's something that people should simply should know due to how basic it is How often do you go to McDonald's and order a 1/4+3drinks/fries(applepie-sauce)?

[Goodwin]

Regardless, if this left/right thing is indeed correct, why in the world would it not be taught?

It is correct and it is taught - I said it wasn't taught to me when I was at school, but that was 26 years ago. I also mentioned earlier in this thread that the teaching of maths in the UK is variable at best: I feel adequately qualified to make such a statement because I've worked in education for nearly 15 years in total, over 2 of which was at undergraduate level where I had first hand experience of the variation in maths education.

This just proves Maths is a complete mess. Or at least the standards.

Maths is fine but the standard of it in, say, the UK is pretty poor compared to, say, Germany.

How often do you go to McDonald's and order a 1/4+3drinks/fries(applepie-sauce)? How often do you go to McDonald's, order a meal, pay for it and just assume the price charged was correct? One would hope that the machine doing the calculation can handle standard arithmetic easily enough but the purpose of Kaotika's thread was to show that there is a distinct lack of consistency between how calculators handle mathematical syntax. And if the people who develop and program calculators can't agree on it, who's to say that other machines are functioning correctly?

More importantly though, who the hell eats Maccie D's apple pies? Aren't they hotter than the surface of the Sun?

[erubresen]

The fact is, we were taught what we were taught, and once taught, common sense has nothing to do with it. Perhaps that's a poor reflection of California's school systems (which wouldn't surprise me).

When you're taught the "wrong" way and your school-required calculators reinforce the "wrong" way, people are going to be hesitant when you try to question something that's been ingrained in them for years.

I asked my mom, who's an elementary school teaching aide, and she was taught parentheses first, then do it left/right. Doing it that way produced the wrong answer according to the textbook the school had.

EDIT: Just looked it up in another elementary maths book, that one says parentheses then left/right. So it appears I was indeed taught incorrectly or have simply fallen back on PEMDAS since I never use order of operations and have forgotten.

I'm surprised this has never come up for me despite being in a doctorate program now...

[Goodwin]

Doing it that way produced the wrong answer according to the textbook the school had.

That doesn't surprise me - solutions in textbooks are the last thing to be checked (if at all) before publication and the sheer volume of mistakes I regularly see in the dozens of books I have to use depresses me no end.

[EmxATW5m]

To get some image of elementary maths (and sciences and reading) teaching quality in different countries, one might check this:
http://en.wikipedia.org/wiki/Program...ssessment#2009

PISA measures 15 years old students level in maths, sciences and reading every 3 years, and focuses on one of the areas each time, 2009 was focused on reading, and 2012 will be on maths again.