Hundreds, tens units

[squashpie]

Hi, Was helping my DS with his maths h/w earlier. He has to add sums like 13+27 together or 37+42. He gets very very confused about which is the tens and which is the units column. I tried taking him back a step, by getting him to add 37 + 2 but he was still getting confused about whether the 2 was a ten or a unit. I was taught, several hundred years' ago, in the column method but they haven't taught him that yet (he's in Yr 2)so I'm a bit puzzled about how to teach him this. He has been doing these sorts of sums on an open number line but now he's supposed to be able to do this in his head and the positioning of the numbers is puzzling him. Any ideas about how I can help him? DESPERATE! TIA!

At school we used arrow cards to help children with partitioning numbers into tens and units.

You would need to print out the tens and units ones onto card. The 'rule' to teach is that you can only make numbers by putting the arrows on top of each other. So, to make the number 42, you need the 40 card and the 2 card. You make the number by putting the cards together, arrows together, and the 2 card covers the zero of the 40 to make 42.

(You can see some in use here

I think the point is, that it is better, mentally, to add 37+42 by doing 37+40 then add on the 2, so he can count up 47, 57, 67, 77, 78, 79...

Hope this helps!

I wouldn't think he's ready to add two digit numbers in his head or with a number line if he is not secure with tens and units.

He will need to do a bit of work with place value. There are loads of games on the internet, such as www.bbc.co.uk/schools/starship/maths/games/place_the_penguin/small_sound/standard.shtml

'Place value' tells us that every number has a 'place'. So the 2 in 27 is in the tens place and is worth 2x10. The 7 is in the units place and is worth 7x1.

Your ds needs to be able to split tens and units numbers into their component parts - i.e. 27 = 20+7.
You can practise this using 10ps and 1ps. You can also buy 0-100 and 0-9 dice which are really useful(e.g. throw a 50, throw a 6: 50+6=56)

The next step from there is the number line, which uses the above knowledge:
37+24:
start at the left of the number line on 37. Split your 24 into 20+4.
Jump on two tens (marking +10 on the jumps and the numbers the jumps 'land' on - i.e. 47, 57)
Do a little hop for the units (write +4 on the hop and write the number it lands on - 61)

(That's hard when you can't draw!!)

Lots of children find the concept of tens and units hard to grasp, and then one day it suddenly clicks. It is absolutely vital they get it though, as lots of methods use the concept as a teaching tool.

Some of this sounds as if I'm teaching grandma to suck eggs - don't mean to patronise if it comes over like that .

Year 4 Maths teacher here.

The example you give of 13+27 should not be tackled until he can do:
2 digits plus 1 digit eg 24+5, 32+6
2 digits plus 1 digit bridging the next 10, eg 24+8, 18+5
then
2 digits plus a multiple of 10, eg 13+30, 26+50

Finally he should be able to do the example you give by either counting on in tens and adding the units or by splitting both up into 10s and units.

We teach this in Year 3 and 4 lower set by the way!

Sounds hard for a Year 2 who is confused about PV (place value).

I'd see the teacher - the homework obviously isn't differentiated and it's going to upset him if he can't do it (and he really won't be able to do it if he doesn't understand TU).
Greenwing has been much clearer than me - you really do have to go through all those stages before doing TU+TU on a number line.

We have spent 4 weeks in my Y2 class (with a bit of fun outside maths in between )going through all the stages and I still have some children on the adding units stage.

Another game for splitting tens and units is target shooting. Get two hoops and some beanbags (or whatever you can find at home!). One hoop is the tens, one is the units. Throw beanbags to make numbers (e.g. 2 bb in the tens hoop makes 20, 5 in the units hoop makes 5. Write the sum 20+5=25)

Here are some good pv games:
www.ictgames.com/placeValue.htm

Thanks to everyone for their helpful replies. He can partition numbers well and understands that, 32, say, is 30+2 and, with an open number line can start with the larger number, bridge through the ten and so on, it's just when he has to do it in his head, he looks at the smaller number and it's as if he gets confused with what the left- or right-hand columns should be (he also gets confused about which is actually his left or right hand, so perhaps it's all related). Perhaps it's just a lot of practice with all this. He has after all cottoned on to the fact that one reads from the left and starts writing from the left, so perhaps he's just got to learn that the tens are on the left?! . Think I'll take him through those arrow cards and also break down this subject into stages as Greenwing suggests and see if it begins to click. I love those halleluyah (sp?!)moments

Why, when doing it in his head, is he thinking about columns? Column addition is a written method. If he's doing 43 + 32, for example, he should be doing 43 + 30 + 2 because he should be able to could on 30 from another 2 digit number. No columns needed.

Is it worth getting him to do it as

30+2 add 50+3... 30+50 is 80... add 2+3 which is 5... 80+5 is 85.

Probably haven't explained it well but it's another intermediate step you can take which I've seen some schools using. Still seems a bit too far ahead though.

I'd reckon he's probably meant to be doing 32... add 50 (can jump along the number line for it in tens)... get to 82, now add on the little bit left in the units 3... 85.

(Disclaimer - I'm half asleep, have eyes gunked up to the eyeballs with cold gunk so am very likely to have ballsed up my maths since I changed the numbers halfway through - you get the idea though)

I wouldn't be going near formal column HTU "sums" yet unless you've been told they're doing them that way.