# Bidmas

Discussion in 'Mathematics' started by Deirds, Jun 20, 2012.

1. ### DeirdsSenior commenter

Hi

Parent looking for help here.
My Yr 8 son was doing MyMaths and I was helping him with something he was getting wrong (6*x^2 not being the same as (6*x)^2. )
I vaguely remembered last year's teacher saying he needed to work on Bidmas. It was Bodmas when I was at school. Would I be correct in thinking I is for Indices? Do they not need to worry aboit O for Of any more? Do the other letters still stand for Brackets, Division,Mulitiplication, Addition, Subtraction?

Thanks

2. ### PaulDGOccasional commenter

Welcome... And you've highlighted why many of us are uncomfortable with teaching "BIDMAS/BODMAS/PEMDAS"...

(Which is that kids remember the word but forget what it means, why they were taught it and that every question is a BIDMAS question!)

Brackets, Indices, Multiplication/Division (equal priorities), Addition/Subtraction (also equal priorities).

Or

Brackets, Order, Multiplication/Division (equal priorities), Addition/Subtraction (also equal priorities).

Or

Parenthesis, Exponentiation, Multiplication/Division (equal priorities), Addition/Subtraction (also equal priorities).

They're all equivalent mnemonics that are intended to help you remember how to deal with the fact that mathematical notation, unlike written English, is minimalist.

3. ### emilyisobel

I use the O for 'other' - covers trig functions etc as well then.

4. ### DeirdsSenior commenter

Thanks for the replies. I will admit that until I got to multiplication I had misremembered D is for Decimal. I corrected it, but it was nearly 40years ago...and I don't think we used it much..

5. ### mathsteacher1953

By coincidence, I was leafing through a revision guide from a well known publisher which said that the O stood for 'over'. Not sure what that is about!

6. ### markussOccasional commenter

I'm no mathematician! I thought the "O" was for "operations". Shows how much I know.

7. ### florapost

i'd go for 'other'as well
but it is a pain - why not just put scads of brackets in - how much extra ink would that us?
i tell pupils it's like putting words in the correct grammatical order in a sentence
but it isn't - it's like talking in yoda-speak with a set of interprative rules
to copy cybola - florapost - in a bad mood tonight

8. ### PaulDGOccasional commenter

You really want to have to write:

(6x) + (3y) - (2z) ??

9. ### florapost

now - that's just being silly
are you someone in my y5 group under an assumed name?

10. ### PiranhaStar commenter

I don't think it works for Trig functions. Sin 2x is usually taken to mean sin (2*x) rather than (sin 2)*x which would be the case if the sine function was done before multiplication.

11. ### emilyisobel

Yes I know, but a function inside another function has invisible brackets like one function divided by another.