Primary school maths techniques

[PaulStat]

Just been doing some maths homework with my son who's in year 2. So early questions were easy enough and I can see the technique they're using for example

addition (add the tens then the ones, tens are the |'s and ones are the .'s)

23 + 11

||... + |. = 34

or a subtraction (remove the tens and ones and then see what's left over)

23 - 11

|.. = 12

Now for the slightly more complicated examples

eg. (addition I got him to write down the ones first and then add an additional ten unit to one side, not sure of the official technique here but it made sense to me and him importantly)

23 + 18

||... + |........ =  1

becomes

|||... + |........ = 41

But for more complicated subtractions I'm not sure how they use this tens and ones technique?

eg.

55 - 37

Obviously I can ask his teacher next week, but does anyone know what methods they teach them here?

 

[PaulStat]

I don't get your 23 + 18 logic.

Surely you you follow the same logic as before but replace 10 dots with a line afterwards.

Once you learn that ten dots and a line are interchangeable, you will realise you can break a line back into 10 dots and hence do complicated substraction.

This does seem like a good way to learn a decimal number system.

Ah yeah duh that does make sense, so using this method it work make more sense like

23 + 18

||... + |........

becomes

|| + ||. = 41

still not sure how they would represent that subtraction though

Not only me that thought this then, It seems to me that that somebody has gone out of there way to find the most complicated way to teach simple maths. What ever happened to numbers on top of each other, counting down and carrying for addition e.g.

  23
+11
=34

For subtractions its the same e.g.

55
37

5-7 = -2
50-30 = 20
20 - 2 = 18.

I guess that I am just a little lost in what it is you are asking?

Yeah that's the way I learnt it too but I don't want to confuse him by teaching him my technique