In elementary school (US) I was taught: PEMDAS =3D Please Excuse My Dear
Aunt Sally

or

Parentheses
Exponents
Multiplication
Division
Addition
Subtraction

Although, I think this is misleading at best. For example, it suggests
that addition should precede subtraction, as in:

3-2+4 would be 3-(2+4) rather than (3-2)+4. As others have pointed
out, this has to do with association and not order of operations.

Sean



On Sat, Mar 10, 2012 at 6:24 PM, Rupert Swarbrick <rswarbrick@gmail.com> wr=
ote:
> Dwayne Reid <dwayner@planet.eon.net> writes:
>> Regardless, I fall upon the old mnemonic phrase for order of math
>> operations that my Maths teacher gave to me way back in grade school:
>> BOMDAS =3D Brackets, then Odd_Functions, then Multiply, then Divide,
>> then Add, then Subtract.
>
> This is amusing to read. In the UK, at least, school students are taught
> "BODMAS" (where "O" stands for "Other", if I recall correctly). Of
> course, since division is just multiplication combined with a (tighter
> binding) reciprocal, it shouldn't matter.
>
> The problem is that it's hard to know how to make sense of
>
> =A01/2/3
>
> (as a pair of quotients, rather than a date, which has its own
> problems!)
>
> This doesn't come from problems of operator precedence, but rather from
> the fact that "/" isn't associative. Fortunately, people make things
> much more obvious when scribbling on paper.
>
> I should say, my immediate interpretation of the above is (1/2)/3, but
> I've spent a significant fraction of my life able to program in C, so I
> suspect that C/Algol/whatever's heritage has more influence on me than
> anything mathematical.
>
> Similar problems arise with 1 - 2 - 3, of course. But (since subtraction
> is always written in one dimension?), the (1-2)-3 interpretation seems
> pretty much universal.
>
>
> Rupert
>
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