How are Number Bonds to 20 useful?

[GreatGooglyMoogly]

DS1 is in Year 1 and has been learning the Number Bonds to 10: 1+9, 2+8, etc, in order to help his mental maths. Now his teacher wants us to work on Number Bonds to 20. I don't really understand how that is useful as surely the Number Bonds to 10 can be used for those to 20, 30, etc?

Number bonds to ten are the basics, but it is a good idea for all of us to have basic addition at our finger tips. Obviously the further you go, the easier it becomes (ie if 9+1 is really easy for you, learning 19+1 will be easier still!).

GreatGooglyMoogly:

The stumbling block for many children in Y1 (and sometimes in Y2) seems to be adding and subtracting over 10. Learning number bonds to 20 - helps them to learn (through memorisation) what happens when you add over 10 - so 10 + 10 = 20, 17 + 30 = 20, etc... Or take away from 20 - so 5 less than 20 is 15, 6 less than 20 is 14, etc...

Once they can work out how to make 20 (for example the number bond 17 + 3 recalled relatively quickly) - they are then well prepared to make 30, 40, 50, etc... And it then becomes an easier jump to make 53, 79, etc...

So for example if given the problem 57 + 8 = 65. The 10 number bonds (but also knowing how to carry from the 20 number bonds) mean they should learn to mentally do this in two jumps (so step 1: 57 + 3 [recognising two things: that 3 + 7 will make the 10 and 3 + 5 = 8] & step 2: 60 + 5 (because they've already used the 3 from the 8).

Hope that helps.

sorry - should have been 17 + 3 = 20.

also useful with taking away and addition to teach the myriad of ways this can be said & how it can be written:

+: plus or x add y or x more than y

-: subtract or x take away y or y less than x

because the teachers/ TA and the SATs will say/ present this in a number of different ways.

PastSellByDate - my DD, who has done number bonds to 20, would calculate 57+8:

7+8 = 15

15 = 10 + 5

50 + 10 + 5 = 65

Bonsoir:

You make a good point. Your daughter's way makes great since to me - but many schools just teach to the exact 10 or the exact 20 - so don't teach all the bonds between (e.g. 15 = 1 +14, 2 + 13, 3 + 12, 4 + 11, 5 + 15, etc....) - the result is that many children can initially lack the ability to see these other number patterns.

So what seems to be happening - is that children are taught bonds to 10 (1 + 9, 2 + 8, 3 + 7, 4 + 6, 5 + 5, 6 + 4, 7 + 3, 8 + 2, 9 + 1) and exact bonds for 20 - but not taught all the little numbers between. End result is that it can be more tricky for children to work out the numbers between (easier to make then 10 and then add remaining number less than 10 - because children have also been taught to add to 10 - i.e. 10 +1 = 11, 10 + 2 = 12, etc...).

Why schools aren't teaching all the numbers between ( so children know all ways to make 8 (1 + 7, 2 + 6, 3 + 5, 4 + 4, 5 + 3, 6 + 2, 7 + 1) or providing that practice in homeworks is a mystery to me (clearly not happening at our school at least).

sorry - should be great sense. Tired today.

I think the way my DD is being taught focuses very strongly on place value, and getting the children to think in terms of tens and units (and, now, hundreds and thousands too).

Bonsoir:

Sounds like you are at a school where math is taught well - with focus on number patterns.

Sadly DD1 had 12 pieces of maths homework in entirety of KS1 (3 years) and place value at our school is only introduced in Y4. Sigh...

You can see why we gave up and went over to Mathsfactor.

Yes, it probably is being taught quite well at school. We do supplement a bit - DD has a tutor for one hour a week, who alternates maths and literacy and fills in gaps as DD is in the French system and although the school is bilingual, the English is a bit dodgy. So this keeps her up to speed with England and also gives her a bit of an extra boost.

Bonsoir
what class is your DD in now?

She's in 10ème/CE1/Y3. Though, like your DD1, she is an Autumn baby and would only be in Y2 were she in England.

How is your DD getting on with phonics and reading? Is it well taught?

I agree with you that learning 19+1 is not adding anything if you have already learnt 9+1, but i think number bonds to 20 are v helpful where it crosses a 10, i.e learning number bonds to 10 does not help with 7+5 (and in tun 27+25 etc), so you need to do up to 20 to pick up that. (ie that were you have a 7 and a 5 in the units you end up with a 2 in the units and an extra 1 in the tens)

Slight confusion here too, but not so much with bonds up to 20, DD Y1 is very good with those adding and taking away with ease up to 20, my dilemma is more to do with the ways I am teaching her at home to build up adding above twenty.
E.g I teach her 24+
26
-
50
She will add 6+4 write 0, remember 1 which she will then add with 2+2 and write 5 to get 50 as her result, she is getting it no problem, but Is this the way that is still practised in schools? or not

Bonsoir
DD is loving SIS and reading brilliantly. Jolly Phonics plus Read Write Inc has been a very easy way to start reading. She is reading simple English books easily and fluently and blends really well. Best of all, she loves it. Her SIS teacher is fab. They are doing regular English dictation and so it is really quite challenging. V. pleased even though we have to leave the house at 7.15 on Wednesdays for SIS. There's tons if homework but DD1 thrives on it. (Ok, she is motivated by a star chart, but rarely needs asking twice).

Can't wait to get DD2 in, but they don't start until GS and she doesn't start PS until this Sept so some way to go yet.

The way my DD would do 24 + 26 is

4 + 6 = 10

20 + 20 + 10 = 50

Greythorne - that sounds fabulous and I just wish EaB could get its head round teaching the Anglophone children to read in GS, rather than waiting for CE1. I'm so pleased for you and your DD1 and well done her!

thanks Bonsoir,

Getting children to count in tens and understanding place value (tens and units to begin with) is very useful, IMO. They can then do lots of practical things like cooking (weighing and measuring with old-fashioned scales and metric weights) and measuring (buy some nice rulers) and adding up the cost of small items - great to have a toy cash register and pretend money.

One more question Bonsoir, Does it matter if at home we are adding two digit or three digit numbers in column with line underneath, rather then in line with equal (=) at the end of it?
What is the school preferred method, if you know?
If this makes any sense to you?

DC need to learn both. Column addition is an important skill. There are lots of ways of thinking about arithmetic!

That makes sense, thanks.

GreatGooglyMoogly you are correct if a child knows number bonds to 10 and place value they don't need to learn number bonds to 20 but it's there in the framework so schools teach it.