BIDMAS

11 Plus Maths – Preparation and Information

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JaneEyre
Posts: 4843
Joined: Sun May 09, 2010 1:04 pm

Re: BIDMAS

Post by JaneEyre »

I agree with you, Guest 55! But the point that users of BIDMAS have to realise is that addition does not need to be done before subtracting nor multiplying before dividing. So this mnemonic technique is not perfect, though maybe helpful.

But it is true that the person doing the calculation has to take the easiest route! ... and remember that maths is fun! :wink:

crossed message with PurpleDuck
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: BIDMAS

Post by Guest55 »

I think any 'error' will come from an imperfect understanding by a teacher which is then 'passed on'.

It's common to 'play' with the order of addition/subtraction at Primary to show order does not matter. Ditto with multiplication/division - it's when you have a combination that you need to beware.

Everyone knows maths is fun :)
yoyo123
Posts: 8099
Joined: Mon Jun 18, 2007 3:32 pm
Location: East Kent

Re: BIDMAS

Post by yoyo123 »

I think any 'error' will come from an imperfect understanding by a teacher which is then 'passed on'.
True, not just for maths either.

I often think I have spent my career correcting misconceptions.

Incidentally, the new Target maths Y6 books now refer to BOMDAS.
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: BIDMAS

Post by mystery »

We had lots of "ors" in it when we learned it at school

Brackets followed by

Indices followed by

Division OR Multiplication followed by

Addition OR Subtraction


The biggest issues seems to be not giving practice in a variety of topics all the time to keep all the maths skills learned to date fresh. Old curriculum, new curriculum, primary school, selective school ........ not great planning in my personal experience, poor resources.

No-one seems to own a decent maths textbook these days which contains practice problems which will regularly use the skills the child has learned so far. So the novice BIDMAS user becomes like a poor skiier who skis 3 days each year and spends those 3 days getting back to the point they were the previous year.

And Hera - look at how badly you must have been taught maths. They're supposed to have taught you that kind of thing long before O level / GCSE. But you grasped it easily enough on here despite what must have been many wasted years in school maths lessons where simple mathematical logic was missed out. What is/was going on in those classrooms?
Last edited by mystery on Thu Mar 10, 2016 1:52 pm, edited 1 time in total.
Proud_Dad
Posts: 500
Joined: Fri Oct 11, 2013 9:55 am

Re: BIDMAS

Post by Proud_Dad »

Guest55 wrote:I disagree - sometimes there is a 'most efficient way of calculating:

25 + 7 - 5 is best done in the order 25 - 5 + 7 which is quicker than tackling in order.
Yes that's true and is useful so long as you remember not to get the signs messed up. And being able to do that actually relies on the fact that the order between addition and subtraction doesn't matter, which is what confused the OP in the first place.

The acronym could just as well be BOMDSA (although wouldn't be as easy to say! :) )

This link shows a poster which I think explains it quite nicely.

http://themathsmagpie.blogspot.co.uk/20 ... ption.html" onclick="window.open(this.href);return false;
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: BIDMAS

Post by Guest55 »

The poster is still poor though - as in my example, reading left to right is not necessarily the 'best'.
Hera
Posts: 856
Joined: Mon Feb 22, 2010 3:50 pm

Re: BIDMAS

Post by Hera »

And Hera - look at how badly you must have been taught maths. They're supposed to have taught you that kind of thing long before O level / GCSE. But you grasped it easily enough on here despite what must have been many wasted years in school maths lessons where simple mathematical logic was missed out. What is/was going on in those classrooms?
I did in fact have an excellent teacher for my O-level maths and did rather well; but that was 30 years ago. I am sure that my 16 year old self would have had a strong grasp of the concepts and now I am sure I will never forget it! :oops:
PurpleDuck
Posts: 1586
Joined: Sat Jul 24, 2010 10:45 pm

Re: BIDMAS

Post by PurpleDuck »

yoyo123 wrote:Incidentally, the new Target maths Y6 books now refer to BOMDAS.
I have come across BODMAS before, but not BOMDAS... I sense opportunities for some mispronunciation of BOMDAS among Y6s and a lot of giggles coming out of that. :lol:
It felt like I hit rock bottom; suddenly, there was knocking from beneath... (anon.)
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: BIDMAS

Post by Guest55 »

Hera wrote:I did in fact have an excellent teacher for my O-level maths and did rather well; but that was 30 years ago. I am sure that my 16 year old self would have had a strong grasp of the concepts and now I am sure I will never forget it! :oops:
I thought mystery's post was quite rude - many people forget this sort of thing.
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: BIDMAS

Post by mystery »

Hera wrote:
And Hera - look at how badly you must have been taught maths. They're supposed to have taught you that kind of thing long before O level / GCSE. But you grasped it easily enough on here despite what must have been many wasted years in school maths lessons where simple mathematical logic was missed out. What is/was going on in those classrooms?
I did in fact have an excellent teacher for my O-level maths and did rather well; but that was 30 years ago. I am sure that my 16 year old self would have had a strong grasp of the concepts and now I am sure I will never forget it! :oops:

Oops! Apologies to your maths teachers over many years then. I'm probably wrong but my feeling just is that if it's been sufficiently reinforced over many years at school it wouldn't have gone away either but I suppose it's not the kind of thing that people necessarily give one thought to again once O' level is out of the way.

But again, I'm finding that the way they do it at school is to repeat loads of addition at the start of each term, then a load of subtractions for a few weeks, and then towards the end of the year throw in a mixture and some negative numbers as the icing on the cake to be forgotten again until a similar point in the following year. Not good enough. Division is a poor tacked on late in term or year topic as well. Sorry if that's rude but it's my children's poor experience. Hope other people's are better.
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