How do you teach subtraction from 20? (Year 1)

[Twiglett]

DS doing money

Homework this weekend was adding to things to get total then seeing how much change out of 20p .. no issue with the working out the adding .. but much difficulty with working out the change

I tried to show him how to count on (ie hold 13 in his head then count on his fingers till he got to 20)

I tried to show him with actual money .. so I had a 20p piece and he had loads of change

but he still seems a little confused

have written a note to teacher to ask but does anyone know cos we're doing a few more this morning

AFAIK we're doing it the same way, but there is a clear break between doing the sum, and working out the change. So ds writes down the sum (and st present it is through counting on/number line), and then when he sees that the answer is 7p (and he has written this down!), he then works out which coins add up to 7.

teacher said they use a number line .. which is a line with the numbers 0 to 20 marked on it

and they teach them to work backwards ... but I couldn't work out if they count backwards from 20 going 1, 2, 3 or by saying 19, 18, 17 .. and if latter how would they know

I have asked her for a sheet on it

I think it should be pretty self-explanatory that they do a sheet to parents to explain HOW they are teaching in class otherwise how can we possibly support them at home???

we were given a booklet from DS's school (I think they gave them to all the primary kids) - explaining how maths is taught now.

The number line was part of it - but I can't remember if it was 19,18,17 or 1,2,3 - I would be inclined to do 1,2,3 and then go back and say - or you could do 19,18,17 - and talk about what is different about the two approaches. That way you are playing with numbers and getting a feel for how things fit together.