Year 6 maths...

[FermatsTheorem]

Can anyone help me decipher a partially remembered acronym?

DS says he's struggling with something he says is called "XNMP" - but google isn't helping, which makes me think he has mis-remembered the acronym.

It appears to be something to do with cross multiplying, i.e. (hope formatting works)

a/b
___ = a/b * d/c
c/d

Once I know what he's actually on about, I'll have no trouble (am v good at maths) - it's just working out what it is that he's stuck with.

Thanks!

I remember how I taught dd to divide by fractions.
Draw a numberline, say 1 to 12.
Divide it by chunking, So how many lots of three can you take out of it? (count back in groups of 3 to find you can get 4) So 12/3=4.

How many 1s can you get out of it? Again show 12/1=12

How many halves can you get out of it? Draw on the jumps back of a half to show 24. So 12/half=24. So they can see for every number they get 2 jumps back. So the number doubles. Once they have got this, you can then move on to dividing by1/4 1/3 etc. Once they have got that show them how jumps of 3/4, three times bigger, will mean 3 times less jumps.

Hopefully, knowing why should make the formula easier to remember.

I remember doing similar with my ds Richmal.

It was a volume question. How many 1/4 shape can you get out of the
1 1/2 x 3 1/4 x 4 cube, something like that. We used the number line working out how many 1/4 you can get out of each sides.

I think fraction division is not very instinctive, until you realise what is really happening.

I don't think it is instinctive either. My guess is that if you asked most adults what 12 divided by a half was they would say 6.

• cube, shape! Not a cube obviously!

I must confess, despite somehow managing to get an A in GCSE maths (1993) I had never heard of BIDMAS/BODMAS until a few years ago . I must have been taught the principle as I clearly use it.

Did we call it something different then? Or was I just chatting too much to my mate at the back of the class when we covered that bit?

I like that Richmal. Visualisations are always good.

I'm glad you like it. I could never see why people thought maths was boring, when to me it was about playing with patterns. I think I have the same attitude as irvineoneohone when teaching dcs maths; keep it bright, make it visual and don't just teach how, teach why.

That's why I'm so convinced DS isn't actually bad at maths - he has a really good intuitive grasp of pattern and symmetry. It's just that SATs is sucking the joy out of it all. (The secondary we've put down as first choice, the maths teacher gave a little talk on the open evening saying a lot of the first year maths course was devoted to pattern and geometry and making maths fun again after the damage done by SATs and I felt like running up to him and giving him a hug ).

Fermat, a lot of people say they are bad at maths, when they actually mean they are bored silly by arithmetic. It sounds like your dc will be going to a good secondary for maths teaching.

Just on the bidmas thing, I could not remember learning it at school either. I always just use the rules as they are easier than the acronym for me too. I know O is for the power raised to, but not sure what the word is. I always see the brackets as being a little box you can move around and open later in algebra.

Dividing by fractions becomes easier to see if you convert the fractions to a decimal- eg 12 divided by 0.5 is easier to visualise than 12 dived by 1/2.

I am not totally sure if decimal division is easier or not. That's another trick they learn to do, by moving decimal point.
Do they really understand what they are doing?
12 divide by 1/2....how many half an apple can you get out of 12 apples, is easier to understand than 12 divide by 0.5.
Anyways, I do agree, visualisation is the key to understanding what is going on, and without proper understanding, it will be superficial understanding of both fractions and decimals

The other thing about decimal division (nitty picky point about pause maths coming up) is that you lose a sense of the Idea of the multiplicative identity and of reciprocals. (Also ultimately the distinction between the rational and irrational reals).

Probably not needed at this age, but it hurts to think of all that beautiful maths being misrepresented...

(Though I admit that's possibly beside the point when it comes to showing DS how to do it... On the other hand I can imagine a mathematically curious child of this age getting a huge kick out of Cantor's first and second diagonal arguments - they certainly get fascinated by the infinite earlier in my experience, and the idea that some infinite sets are bigger than others, well as DS loves saying during Dr Who, "Mind blown!!!").