Helllp - i can't get my head round partitioning (primary maths)

[LEMisdisappointed]

So, it seems logical for addition and simple subtraction, but i don't know what to do when you have to subtract something bigger from something smaller. So if i am doing it right an example would be:-

4300-2600 = ? ,

4000-2000 = 2000,
300-600 = ??? ,

My DD seems to favour the HTU method and understands exchanging/borrowing and we did it that way in her homework. The thing is, the school has changed (under pressure from the demon ofsted) its methodology policy - they used to say whatever method works best for you. Now they are wanting to stick to one method and apparently there is a push for more "mental" type methods. Partitioning is what they use - I can't see how to do it this way. Am i missing somethng?

Sorry, should have said - this is for year 4.

My DD does struggle with maths and literacy as she is dyslexic.

I teach it by just partitioning the second number

4300 - 2000 = 2300

2300-600 = 1700

Seems to work!

for something like that in mental maths you probably wouldn't do partitioning you would instead count on- so 2600+1000=3600, 3600+400=4000, 4000+300=4300, 1000+400+300=1700

someone that was ok with negative numbers and number bonds to 20 could to 2000 + (300-600)= 2000-300 = (20100)-(3100)=17*100 = 1700

btw mental maths always makes me think of a david brent Christmas party

You leave the first number alone:

4300-2600 (2000,600)

4300 -2000= 2300

2300-600= 1700

thanks!

lougle that method seems the easiest to me, i think!

Ah, now you mention counting on, i seem to remember that from the meeting i went to i am getting old!

I think i'll go and bother DDs teacher tomorrow and see how he wants them to do it. I don't want to confuse her with my confusion :)

As previous posters have said you can't partition both numbers as you can with addition, you need to do subtraction as lougle has done it.

I am 43, my DD is 8, I have a PhD in biochemistry and i still couldn't get my head round the hard ones at the end, so.........

I let her do the last five sums on her own with no imput from me - she devised a little method all of her own (i suspect she remembered from school) and explained it too me - i had to use a calculator to check but she got them all right

I have turned into one of those parents who can't do numbers! i need to get a job before my brain turns to total cabbage

It's just a completely different way of recording your workings.

In reality, it's what you would do for a really tricky sum.

16323 - 14879 (14000, 879)

16323 - 14000 = 2323

2323 - 879 (800, 79)

2323 - 800 = 1523

1523 - 79 = 1444

If you got stuck at the 1523-79 stage, you could further partition:

1523 - 79 (70, 9)

1523 - 70 = 1453

1450 - 9 = 1444