Adding tens and units in years 2 and 3

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fatbananas
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Joined: Mon Mar 08, 2010 2:03 pm

Adding tens and units in years 2 and 3

Post by fatbananas »

With sums such as 25+24, or 36+11, are children encouraged to add the tens together first and then the units (looking out for number bonds as appropriate), and then adding together? Or do they work from a mental number line, adding 10s first and then the units (how would this work with number bonds such as 22+38, for eg?).

And when do they learn column addition?

Thank you! :)
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inkypinkyponky
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Location: Gravesend, Kent

Re: Adding tens and units in years 2 and 3

Post by inkypinkyponky »

I can only tell you the way my son in Year 3 would add these numbers.

25+24 would be added together in his head by taking the 25 adding 2 lots of 10 then the 4 units

So 36+11 would therefore be 36 add 10 then add the extra 1

I know lots of children would add the whole 2nd number in a flash, but my son is average at maths, not super-clever, so he finds it easier to break the numbers down to start with.

As to whether this is the correct way or not, parents don't get to meet the Maths or Literacy set teachers until February!

Edited to add....sorry, I have no idea about column addition.
mystery
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Joined: Tue Jul 21, 2009 10:56 pm

Re: Adding tens and units in years 2 and 3

Post by mystery »

They are encouraged to do it lots of different ways - kind of depends on the teacher.

The way that I find mine are fastest .... until it gets undone again is only to partition the second number

so

56 plus 48

say in head 56 + 40 = 96

Then add the 8 to get 104

Can do same thing no matter how many digits and no carrying is really needed in your head. Can subtract the same way. i.e. first take away the thousands, then the hundreds then the tens then the units.

If they are crossing a "boundary" --- like 512 - 30 they might be thinking about it lots of different ways ...... guess you would practise by doing 510 - 10, 20, 30, 40 etc first.


They are supposed to do loads more mental arithmetic like this in the new national curriculum. Have you had a read of it year by year? But they don't prescribe how to teach it.
inkypinkyponky
Posts: 1863
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Location: Gravesend, Kent

Re: Adding tens and units in years 2 and 3

Post by inkypinkyponky »

I am very embarrassed to admit that I've just realised my son actually started in Year 4 last month! :oops:
fatbananas
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Joined: Mon Mar 08, 2010 2:03 pm

Re: Adding tens and units in years 2 and 3

Post by fatbananas »

Thanks Inkypinkyponk and Mystery! That's v helpful.

Don't worry Inky. I do exactly the same! :)
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Guest55
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Re: Adding tens and units in years 2 and 3

Post by Guest55 »

Yo might want to look at the new Primary National curriculum - I think columnar addition is in Year 3.

https://www.gov.uk/government/uploads/s ... _FINAL.pdf" onclick="window.open(this.href);return false;
fatbananas
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Re: Adding tens and units in years 2 and 3

Post by fatbananas »

Thank you guest55.
Seize the day ... before it seizes you.
Guest55
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Re: Adding tens and units in years 2 and 3

Post by Guest55 »

Two digits numbers are done mentally and it's only when you have three digits or lots of two digit numbers that some people would use column addition.

Questions are always set out horizontally at KS2 and GCSE so children/students are free to choose their method. Lots of my students do all addition mentally unless it is awkward.

24 + 25 is known as a 'near double' as the two numbers are close. You can double 24 and add 1 or double 25 and subtract 1 or .....
fatbananas
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Re: Adding tens and units in years 2 and 3

Post by fatbananas »

I see; thank you. That's really helpful.
Seize the day ... before it seizes you.
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: Adding tens and units in years 2 and 3

Post by mystery »

Yes, and with numbers ending 7, 8, or 9 child might be quite fast using the nearest multiple of 10 and then adjusting afterwards.
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