Any teachers about that could reassure me re how I'm supporting y4 dd with subtraction?

[Retropear]

Bizarrely subtraction has always been an issue- addition,multiplication and division are fine.

Anyhow she asked me to help her with subtraction as she got some wrong at school yesterday.I went through all the techniques(number line,splitting the numbers up etc which she can do but gets into a muddle with bigger numbers) and the only way that seems to work is when she gets the smaller number up to the bigger eg with 90-26( I said get up to the nearest 10 so 30 by adding 4 then adding on 60).

She seems to have cracked it that way however dp says we're still skirting round the problem.Thing is now she's in year 4 tbf if it works I'm of the opinion lets run with it.

Yay/nay?

The last yr3/4 maths lesson I observed they would work a subtraction sum like 92-37 like this....
37+(choose a number)=
37+20 = 57 (not big enough so add another number of choice)
57+20=77 (not big enough so add another number of choice)
77+ 10=87 (still not big enough...)
87+3=90 aha I know how to get to 92 now...
90+2=92

Now I add up all the numbers I have chosen so
20+20+10+3+2=55
so
92-37=55

Hi Retropear

I'm just a Mum but my DD1 had terrible struggles with subtraction and only really cracked it in Y4 if that's any reassurance.

My advice based on our experience is this:

1. There may be an underlying weakness with number bonds (especially in reverse).

So maybe she knows all the ways to make 10 but hasn't really got that instant recall to make 9, 8, 7, 6, 5, etc... when in fact they're as important.

So our solution were these:

Play snakes an ladders with 2 dice & backwards. Roll two dice (say you roll 9). What is 100 - 9. Have your DC count back at first. But then gradually encourage jumps. Logical things to encourage are thinking about making tens. So if it is 87 - 9 - what would you take away from 87 to make 80. '7' - OK so if you use up 7 of your 9 moves, how many are left - may have to count out but the answer is 2. so you can do this in two jumps. 87 - 7 = 80 and 80 - 2 is = 78. You can double check this by counting all 9 moves individually.

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We played a lot of 21 or black jack. Basically having to work up sums to 21 gives a lot of practice with different number bonds.

How we played: Deal 2 cards to each player face up. Card values: Ace = 1, 2 - 9 as shown, Jack/ Queen/ King = 10. So total up your two cards. Say your DC gets Jack and 3 - DC has 13. The object is to get 21 or as close to 21 as possible. If you go over you're out. So have your DC decide whether to have another card or not. Say s/he does and it's a 7. So Jack + 3 + 7 = 20. That's about as close as you're going to get.

At first it's very slow and you'll have to talk it through a lot but speed will improve.

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You can play number bond snap. Just take the number cards from a deck - have a target number (for addition or subtraction) - and then flip over the card. Fastest person to answer wins the card. The winner of the game is the one with most cards. (May be an idea to let them win at first to build confidence!)

So working on subtraction. Start with a nice easy target - say 30.

Flip the card. Say it's 9.

30 - 9 = ?

Be patient but let them work it out. If this is where it all goes to pot - have them do it with visual clues. We use grapes and raisins. 10 raisins is = to a grape.

So 30 is 3 grapes and 9 is 9 raisins. Put the three grapes on one plate and the 9 raisins on the other. Now the problem is obvious. You don't have any raisins to work with. You have 3 grapes or 3 tens but 0 raisins or 0. So cash in a grape for 10 raisins. You now have 2 grapes and 10 raisins. You can work with those raisins now.

Take away 9 raisins (we tend to make two rows of raisins - so each raisin from the '30 plate' matches the raisins from the '9' plate.

What do you have left on your original '30 plate' - you have 2 grapes and 1 raisin - so 30 - 9 = 2 grapes and 1 raisin or 21.

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Once your good with 20 or 30 - then try the other multiples of 10 to 100. (40, 50, 60 ....100).

Once that's sound - then get evil. Try 89. What's 89 - 5? 89 - 9? etc... numbers ending in 9 is a good starting point because no number will be bigger than 9. So no borrowing.

Once that's good you're going to have to deal with borrowing - which really isn't a big deal because you've been there with multiples of 10.

Start with 5 times table - so try 45 - ?

Really get your DC to work with number bonds up to 5 (1+4, 2+3, 3+2, 4 + 1) and making bonds with 5 - (so 5 + 1 = 6, 5 + 2 = 7, 5 + 3 = 8, etc...) - these basic bonds will be key to working out answers.

So say you flip 8. What is 45 - 8?

Well if we think about 8 as 5 + 3 - we can do this in 2 steps.

45 take away 5 is 40. 40 - 3 is? (hopefully that number bonds of 10 thing/ or grape & raisin work with multiples of 10 will come back into play) - and you should get 40 - 3 = 37 - so 45 - 8 = 37.

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We did a lot of this 'for fun' over Christmas Year 4 and evenings in winter of Y4 - and it seemed to really help improve underlying basic maths skills and before we knew it there was no more 'issue with subtraction'. We still play occasionally for fun as a family - but it's a bit more cut-throat now - with serious betting of smarties and much pouting when Mum loses.

I should add that it really is important that your DC learns that there are units, tens and hundreds and that they all have to be dealt with one at a time (especially in subtraction).

I also highly recommend subtraction games on Woodland Junior school Maths Zone (and maths zone in general) here: resources.woodlands-junior.kent.sch.uk/maths/numberskills.html or Bop a bot games on Maths Champs: www.mathschamps.co.uk/games5-7?.

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Our final step was introducing 'traditional' vertical subtraction.

HTH

It's a perfectly acceptable method. In fact it's pretty much the only one I ever use when doing subtraction mentally. I would say as long as she understands subtraction itself, can identify when to use it to solve real life problems and has one failsafe way of subtracting mentally she will be fine.

I might continue to work on partitioning a bit to help her understand the formal written method in future but in terms of mental strategies there's no use forcing the issue if she really doesn't get it and has an effective method already.

'counting on' is good for 2 big numbers or if the numbers are close together.

if one number is much smaller than the other then subtracting is simpler in the long run.

both methods can be done mentally or with a number line.

if she has a method that works that's fine.

with written methods she will eventually move to column subtraction, but that's not a good mental method.

LittleMissGreen were the kids writing that down, or doing it in their heads? Either way it seems an extraordinary long-winded way of doing it!

They were writing it down. I was that takes ages, I think I need a school maths lesson! But the other person I was with (a teacher) said "Yes this is how we teach it too".

In the Autumn term of Y4, subtraction is usually taught through counting on. (e.g. 57 - 23 would be either counting on in 10s - to 33, 43,53 and then the additional 3, or count on TO the next 10, as in add 7 to get to 30, then to 40, 50 and the extra 7).
Standardised column methods (Tens and Units) are usually introduced in the Spring term.

So is that what I did Clam?

Thanks all for the advice.Past will check out your links,many thanks.

Oops, add the additional 4 I should have said!