What mathmatical method should a Y1 use ...

[brassband]

to add 15, 10 and 5.
DD has just started at a new school and said she didn't understand the teacher's explanation of how to go about it.Not in any way upset, but I thought I would like to practise it with her as the teacher is going to be off most of next week

Could do it in different ways in Y1.

One way:

15+5 = 20 (number bonds to 20)
20+10 = 30 (add on in 10s)

Second way:

15+10 = 25 (add on in 10s)
25+5 = 30 (number bonds again)

Third way:

segment 15 = 10 and 5
10+10 = 20
5+5 = 10
20+10 = 30

All would be pretty much valid in Y1. they won't be doing column maths yet though.

Which way has she been shown?

She doesn't know!
She was talking about 20-16=4 and 20-4=16 earlier in the week though, which sounds like she is doing number bonds to 20

I hope this isn't a hijack (actually, I know it is, sorry!) but why is column maths so frowned on? It just seems os easy!

It isn't frowned upon, but nowadays children are taught a number of strategies which help them with numeracy in general. Being able to do column addition means that you can always work out the calculation is you have pen and paper, but other methods are better suited to mental maths say.

I can do mental math very fast and accurately by doing number line stuff -- I taught it to myself as an adult long before I ever heard of such a thing in schools. Funny enough most the home-edders I know hate number lines, I really don't get why.

I Can't mentally do column maths for shit, even though it's the only way I was ever taught in school.

One of the promblems with just doing column calculations, seeker, is that children usually have little understanding of what is going on. They remember to add this column and that column (which is fine) but soon forget that they are adding tens or units or hundreds. So mental calculations helps some children to imagine numbers, and work well with numbers, in their heads.

And some children prefer mental ways of multiplying 52 by 6, for example. So it's important to teach a range of strategies so that children can realise which ones they prefer and which ones make most sense to them.

seeker - int he exp through my DD they start doing column maths in Y3, once they understand how the numbers all work together, etc. Once at that point they are shown all the otions and can chose the ones they feelwork best for them, DD finds column maths the most effective for her. I admit to showing her earlier on as I suspected it would.