method for calculating long addition in Y2?

[violetbloom]

Looking at dd's homework, there are numbers like 47 + 59 = / 347 + 257 =

I was trying to show dd how I used to do it at school but she says they don't do that when it comes to carrying over a 10 or 100, but couldn't tell me how they do do it! Is there a standard method these days?

Have just asked dd (y2)
She did this:

47 + 59 =
40 + 50 + 90
7 + 9 = 16
90 + 16 = 106

So 47 + 59 = 106

So it looks like they partition the numbers down into hundreds, tens and units and then add up like with like. Then add the answers from this together to get to the final total.

Just noticed a mistake, first line of calculations should be:
40 + 50 = 90

Wow. I'm not sure how I feel about them changing that.
The hundreds, tens and units columns and carrying over seemed to help with understanding numbers.
If this is how they do it now, then no wonder they put a lot of time into the number bonds thing.

Although, I admit that new way is how I do it in my own head when shopping or whatever.

Can I ask the method for taking away e.g. 146 - 37. Thanks.

I guess you would find how much you need to add to 37 to get 146 i.e. 3 to get to 40, 100 to get to 140, 6 to get to 146, so 109

or use compensation
146 - 37 = 146 - 40 + 3 = 106 + 3 = 109

I am always interrested in these threads as I home educate my Y2 ds. I tried teaching him that way, but it was just such a faff for both of us, I prefer adding in coloumns - how used to do addition/subtraction at school as so does ds.

Or number line for addition and subtraction

Biggest number first so
+1 +40 +6
59 60 100 =106

Add on to subtract so

+3 +100 +3
37 40 140 146 ; then add top line to get answer - 3+100+3 = 106

HTH

Sorry, missed final 3 answ = 109

Thanks everyone! Gherkin I haven't got a clue what your calculations mean! I am actually very rubbish at maths. I can just about get what hippi said although I have to say I find the columns way easier ...

So for the sum 347 + 257, how would you do that with the hippi method?

300 + 200 = 500
40 + 50 = 90
7 + 7 = 14

500 + 90 = 590

590 + 14 = (but then you'd still end up with a ten carrying over from the ten of 14 ...)

And how would it work with even larger numbers, say, in the thousands?

You would break it down (partition) again if you needed to so:

590 + 10 = 600
600 + 4 = 604

So even with HUGE numbers as long as you partition into thousands, hundreds, tens and units etc it still works. If the numbers are too big to handle you just partition again IYSWIM (like in the above example).

590 + 14 = 590 + 10 + 4 = 500 + 90 + 10 + 4 = 500 + 100 + 4 = 604

you know that 90 + 10 = 100
similar to 9 + 1 = 10

same principle for 1000s

7645 + 4528 = 7000 + 600 + 40 + 5 + 4000 + 500 + 20 + 8 =
(7000 + 4000) + (600 + 500) + (40 + 20) + (5 + 8) =
(7000 + 3000 + 1000) + (600 + 400 + 100) + 60 + (5 + 5 + 3) =
10000 + 1000 + 1000 + 100 + 60 + 10 + 3 =
10000 + 2000 + 100 + 70 + 3 =
12173

Column addition will come later on. I teach it to my year 4 children. While the partitioning might seem like a faff it does help them understand what they are doing much better and means that later on they'll know what they are doing when using column addition, not just repeating learning by rote.