Number bonds - help

[cassgate]

Ok I thought I knew what I was doing but seem to be confusing my ds so after some help in the best way to teach number bonds to 20, 30 and beyond.

DS is yr 3 and teacher has highlighted a few areas where he needs more practice. Number bonds being the biggest area. Number bonds to 10 are secure and he understands the relationship between the numbers eg doesn't just know that 6 + 4 = 10 can also tell you that 10-4 = 6 and 10-6 = 4, can do this for all pairs to 10. Have been looking at number bonds to 20 tonight and thought he would get it straight away but he doesn't and I am at a loss as to how best to approach it. We started off by writing down all the pairs of numbers to make 20 and I was hoping that he would see the relationship between knowing his number bonds to 10 and how it helps to work out number bonds to 20 but he just doesn't seem to see the relationship. E.g if I ask him 17+ ? = 20 he will say 3 but if you ask him 3 + ? = 20 he will say 7 instead of 17 as he forgets about the extra 10. He is very good at partitioning numbers into hundreds, tens and units and can do addition using this method even when it bridges 10 and he has to carry over a lot of 10 so am confused as to why he is just not getting number bonds to 20. We have been using a website called top marks which his teacher recommended but he was getting frustrated as he kept getting the answers wrong so I need to go back to basics I think but how. Any ideas. Thanks

I should add that I want to avoid rote learning as he rote leant his 2, 5 and 10 times table in year 2 but I discovered by accident in the summer holidays that he had no idea that it was repeated addition. His teacher had said that he struggled to apply his times tables knowledge to problem solving. I was planning to work on this over the holidays and within 10 minutes worked out it was because he did not understand what multiplication actually was. He thought that times tables had to be learnt but not what they actually were or how they could be used. I went back to basics with him to show him and he is much better now but does need more work.

Get out some pieces of dried pasta - or something similar.
Make the numbers tangible.
He'll start to get it once he sees the difference between a pile of 7 and a pile of 17.

Sigh - I see this again and again, with teenagers even. They've had years of learning times tables by heart, but couldn't begin to apply it to the real world.

DD's school made up rhymes to help them remember, although they've only done up to ten so far as she's a bit younger.

They were along the lines of 1 and 9 are feeling fine, 2 and 8 are really great etc.

Try it with money.

10p plus lots of one pence.
20p with lots of ones, then other coins.

Does he understand that 20 is 2 tens?

I agree with the suggestion to practice with something tangible- however I would recommend using something which comes in tens as this will hopefully make the relationship between bonds to 10 and 20 clear, so he can later apply those to 30, or 100 etc. Maybe he could practice with his socks off, using toes as well? Or penny sweets in bags of 10. Or Lidl do eggs in boxes of 10. Then make it clear that 3 + 7 = 10, but he needs another 10 to make 20, so it needs to be 3 + 17 to make 20.

PS- he does understand that 17 = 10 + 7 or 7 + 10 doesn't he?

So wait, this is like look and say but for numbers? Learning sums by heart rather than understanding it and letting the sight-adding (by analogy) come later?
No, they would have been doing lots of physical, visual and practical maths at the beginning, before getting to the 7+3=? stage.

If he's good at partitioning into tens and units then get him to do this with pasta.

To be honest it sounds like he actually does know it but he's treating it just like the 1 - 10 number bonds. Which is fine. Just say after every one 'have you forgotten the extra 10?'. He'll soon learn to ask himself this. Make sure you ask him even when he hasn't so he learns that sometimes the answer is no.