Bidmas again! 9-9+9

[redhat]

I can't believe I am failing to assist my child with year 5 homework!

9-9+9

Is this 18 because you do the addition before the subtraction? (I thought it was this but think I'm wrong)

Or is it 9 because the addition and subtraction rank equally and so you go left to right?

I knew I should have paid more attention in school......

[PurpleDaisies]

And apologies redhat I meant mumsneedwine.

Trying to do too much at once!

[mumsneedwine]

It's BIDMAs !!!

Brackets
Indices
Divide
Multiply
Add
Subtract

In that order. Every time.

[dementedpixie]

It's +5 and -3

[redhat]

Nope. Really it isn't.

I am sympathetic. It threw me too.

[dementedpixie]

No it isn't!! Add/subtract are equal. Multiply/divide are equal. Read the links!!!

[PurpleDaisies]

Can you not see how doing BIMDSA as in my example gives the same result?

Do I need to show you my first class degree in physics which was full of degree level maths?

[dementedpixie]

The answer is 42

[PurpleDaisies]

Thanks demented I'm on my phone and scrolling means it's tricky to keep hold of the question.

[mumsneedwine]

Don't be sympathetic - I teach Maths and can assure you BIDMAs is the order. Have to go teach - I will set your 9-9+9 question to my class.

[dementedpixie]

I wrote it down! Also on my phone

[PurpleDaisies]

You have a maths degree mumsneedwine?

[dementedpixie]

But it isn't correct what you are saying. Maybe you better refresh yourself by reading the links

[redhat]

But if you were correct mums then the answer would be -9

The answer is 9

[INeedACheeseSlicer]

I think people get a bit tangled up with BODMAS/BIDMAS when it comes to addition and subtraction.

It's easier (for me, but maybe I am going to confuse people more) if you imagine that the + or - signs are actually attached to the number next to them. (If a number doesn't have a sign next to it, it is always a +, but we don't normally write numbers as +9, we just write 9)

So what you have here is a +9, a +9 and a -9 and you can put them in whatever order you like, it doesn't matter, you'll always end up with +9.

[dementedpixie]

I did bomdas at school so my order would be wrong by what you are saying

[Quiero]

mumsneeswine, I'm a bit concerned that you teach maths actually . With all the kindness in the world...you're wrong.

Google it if you don't believe us.

[SweetAdeline]

Do you really teach maths mumsneedwine???

[redhat]

Nobody is saying that it isn't BIDMAS, they're saying that division and multiplication are done in the order that they appear because they rank equally and so are addition and subtraction.

so its

B
I
DM
AS

[PurpleDaisies]

Don't be sympathetic - I teach Maths and can assure you BIDMAs is the order. Have to go teach - I will set your 9-9+9 question to my class.

So your class of presumably primary age children will know better than people with degree level maths? .

I'm getting the "somebody on the Internet is wrong" rage so I'm bowing out to plan my a level maths teaching. My students will be amused that there are teachers out there who refuse to point blank believe that addition and subtraction are the same level of operation.

[dementedpixie]

www.mathsisfun.com/algebra/operations-order-calculator.html type ot in her and you get 42

[dementedpixie]

It in here*

[HarveySchlumpfenburger]

I teach Maths

Thank god for that. There I was a bit worried that you might be involved in engineering of something where you might do some damage with your misunderstanding of number/BODMAS.

The answers are 9 and 42.

You can stick to the order of division before multiplication or addition before subtraction but you need to remember that the sign goes with the number after it.

So for 9-9+9 you can either work left to right or do -9+9 which equals 0 not 9 and then add 0 to the first 9.

I'd imagine a significant number of your students will get the wrong answer if you've taught them BODMAS incorrectly.

[Quiero]

I am chuckling a bit at mumsneedwine putting the sum to her class. The class she taught...the wrong way.

We can all have a difference of opinion and I'm all for contrasting views but it's quite hard to argue with maths.

[scaevola]

Did mumneedswine see invisible brackets?

9-9+9=9
9-(9+9)=-9

The brackets are needed to overcome the equal precedence of AS.

[noblegiraffe]

The calculation can be done in any order but we say left to right to younger kids to make sure they use the correct sign with the correct number.

So if it was 10-3+6 and they do left to right they'd get 13, but if you said you could do it in any order they might read right to left 6+3-10 which is wrong instead of 6-3+10 which is correct because the minus goes with the 3.