BIDMAS question - what's the right answer

[Overstating]

7-5+6x13?

Thanks!

No wonder so many kids aren't good at maths when they leave school if they are faced with this sort of shit thing at a young age.

Talk about going out of your way to make things unnecessarily difficult when there's no need for it.

It's 80 (lecturer in a mathematical subject).

If the teacher made a stupid mistake while doing something quickly - well that happens to all of us from time to time. If they actually think it's -76 then that's disgraceful and they shouldn't be teaching maths. This is fundamental stuff.

For anyone confused with the -5, it might be easier to reframe it as

(7) + (-5) + (78)

gosti It isn't unnecessary though as you need it for algebra.

e.g. If y=5 then you have to know 3y^2 = 75 and not 225

Oh and it was BOMDAS in my school.

Op, show the teacher this link.
www.bbc.co.uk/bitesize/guides/zsnycdm/revision/1

Answer is 80 (ex year 6 teacher here)

No wonder so many kids aren't good at maths when they leave school if they are faced with this sort of shit thing at a young age.

The kids cope fine with it. They just need a competent teacher who knows what they’re talking about.

Bloody hell.

So with my scraped grade A at GCSE (a long time ago), I got 80 straight away and was obviously taught and understood BIDMAS correctly.

But posters with A level maths and PRIMARY SCHOOL TEACHERS don't? What a worry.

The vast, vast majority of primary school teachers are fine with this. There must be a few bad apples around.

Michaela use GEMS: Groups, Exponents, Multiplication (with its inverse), Subtraction (with its inverse).

Which shows that not everything that comes out of Michaela is gold. Why replace the well-understood ‘Brackets’ with ‘Groups’?

I go for
Brackets
Indices
Divisionandmultiplication
Additionandsubtraction

Said quickly to make it clear they’re together, drawn in a triangle.

It's 80. How embarrassing for the teacher- but a simple mistake, we've all done it!

I learnt BMDAS (Bless My Dear Aunt Sally) at a 60s grammar school. Some friends at the secondary modern said they'd never been taught it and wasn't needed to pass the maths CSE.

Thanks @Soontobe60 I'll keep that as backup. Wasn't able to get to pickup yesterday but will do today.

It is interesting to see this might not be a totally local issue...

And for the comment about whether DC missed the brackets, it was typed on the homework sheet. Lost in translation is always an option but not this time.

Thank you so much for attempting to explain @Temeraire - but I couldn't grasp at all how the jaune/heune/green French false logic would equate to the BIDMAS v straight arithmetic issue. I'm interested that @PurpleDaisies' calculator came up with the same answer as me.

@Lexplorer I went to a comp in 1970s and we were definitely never taught it. I still managed ot get a B (in the days before A*) at maths O level (GCSE equiv) but would definitely have arrived at the answer 104 if presented with that set of calculations to do.

milliefiori she was trying to explain that BIDMAS (or your acronym of choice) IS the logical way to read mathematics, just the way left to right is the logical way to read English. Someone may have a seemingly logical train of thought why jaune means green, but it doesn't make it so.

PurpleDaisies has said that her cheapo coffee table calculator gets it wrong. Those calculators can only do one calculation at a time and so expect you to know the order of operations. To do the question properly on that calculator you need to do the multiplication first, and then add 7 then subtract 5 (or subtract 5 and add 7).

A scientific calculator which allows you to input multiple commands at once will get the right answer.

The problem with ‘we were definitely never taught it’ is that I’ve had students swear down that their previous teacher never taught them x or y. I always thought the teacher was a bit slack until one year I pointed out that I was their teacher the previous year and we’d definitely done it.

This is primary level maths oh dear, I have A at GCSE but was never taught this!

I bet you were Brown

I was never taught BIDMAS, BIDMAS, BMDAS or any other acronym as far as I can recall. I was, however, taught the rules and understand how it works. I think the danger of using acronyms is that people end up not understanding how it works.

Well I tried to sort today but Tuesday is PPA so teacher wasn't there. I didn't know that because DC reply "fine" and "stuff" to any questions and not at all because I'm a crap parent and can't wait to finish with primary school

Michaela HoD's blog explaining why groups here

If I wasn't picking up year 10s and 11s who are BIDMAS - familiar and could start from y7, I think I'd go with it.

I've just tried to do BIDMAS for the first time in my life and got the answer 80. It's not actually hard, is it? You just need to know the order. So weird. I don't think all the different acronyms help.

I had a colleague come to see me with a similar question with a couple of high ability children after she’d taught this as she had different answers to them! I had to tell her they were right and she was wrong and explain why. BODMAS/BIDMAS is a useful acronym but is confusing if the understanding isn’t there (as demonstrated on this thread where people are adamant addition should be done before subtraction)..

Yes, primary teachers should know this. Problem is, we aren’t all maths specialists. The minimum maths grade for a primary teacher at GCSE is C, the new y6 curriculum isn’t much below that. I struggle with some of the harder grammar bits of y6 to be honest.

OP, I’d go back to the teacher and explain they have it wrong, they won’t appreciate it but they need to know! If they won’t speak to you I’d ask to see the head of maths, it’s important kids aren’t taught things incorrectly. Let’s just hope that teacher isn’t the head of maths themselves.

Brown76 - you must have been taught this if you have an A at GCSE as algebra is based on this premise!

Eg
4 + 7a
You know you need to multiply a by 7 before you add 4.