embarrassingly basic subtraction question

[Vicky2011]

Right, this is where I put my hands up and admit to being an utter thicko with maths :(

Am helping DS with his KS1 maths homework and can't figure out how do to subtraction that involves carrying, when there is a zero in the bigger number. So, on one example we've been given, we need to subtract 97 from 205. So far I've been adding a "10" to the units column and then taking one away from from the tens column, but when the tens or hundreds column is a zero I don't understand how you take one away from it. So on this example I've been getting as far as taking 7 from 15 but then getting stuck at the tens column.

I know that in this example DS could do this with a bit of work in his head by rounding 97 up to 100 and then adding the 3 back at the end but he tends to find that kind of mental arithmetic harder than having a written method so I was left feeling a bit of a buffoon when I got stuck trying to teach him the written method.

Any explanations - the simpler the better - would be greatly appreciated!

Many thanks

I'm also a Y2 teacher and we do column addition and subtraction for those children who are ready but most children would do the 97+3 =100
so 205-100+3=108 method

cupofteaplease most of my state school Y2 class know all their tables and use this to solve division calculations. Most can use column addition/subtraction methods but would struggle with long division (perhaps 2 or 3 children could cope).

mrz - I'm surprised (and rather worried) to hear that your y2 pupils know all their tables as at my DCs school they are still learning tables in KS2. Do you teach all tables up to 10 in KS1 and what method do you find works best i.e. reciting by rote or something else ?

I was taught tables by rote and it seems that today's methods are much more informal, in fact I'm not even sure what method is used but ime it doesn't seem to be effective, or maybe my DCs are just finding it hard to learn them.

Most of my class know all their tables up to 12X with the expectation that all will know 2, 5 and 10 times in KS1. It just so happens this class were eager to learn more. We do a timed tables "test" 50 questions in 5 mins and if all are correct they move onto the next table once 2,5,10 are mastered they choose which to learn and once all are learnt they do mixed table question 2-12 and 60 questions in 5 mins to reinforce learning. We use Percy Parker which the children love.
They have of course been taught that multiplication is repeated addition and had lots of practical experience and have used arrays .

mrz, quick question, sorry OP; would it be feasible for me to explain the column method to my yr2 DD who has mastered other methods? I watch her using a blank number line, quite happily, but sit there thinking how I (old school!) would do it! Just to add, she is a very able girl who picks things up quickly; would her teacher be mad with me? Would you be?

I wouldn't be mad but obviously can't speak for every teacher. Some schools are very rigid in what is taught when so it would probably be a good idea to ask.
I'm afraid I'm "easily led" one of my class asked about decimals so we spent part of lunchtime exploring simple decimal calculations.

Thanks mrz, I've had a vague feeling for a while that my DCs should be better with their tables, I may try some of the timed tests with them.

www.math-worksheets-generator.com/multiplication_facts_worksheets.html

Caughtinanet - my kids were taught all their tables in Year 1 and 2 and knew them confidently.

However, we then changed schools who only focussed on 2, 5, 10 up to year 3, and only now covering remainder of tables up to Y6.

So different schools and different countries have different targets of when children should know them.

I have found that because my DC did learn and understand tables early, that it has helped with all other aspects of maths

"I know that in this example DS could do this with a bit of work in his head by rounding 97 up to 100 and then adding the 3 back at the end "

I think it's really good he can do that - can 'visualise' the numbers in his head rather than just following the rules. He must be 6?? Pretty good for that age I think

I am totally perplexed as to what they've done to primary school maths...no column addition until KS2?! It's not like it's hard - unwittingly I've done it with my y2 DS and he hasn't said that's not how they do it, and he hasn't struggled either. But seriously, if schools are going to use new fangled methods they ought to teach it to the parents first, or else we'll teach it all wrong at home!

Children need to fully understand place value and mental calculations before they move on to columns.

If they dont practice mentally at first and understand how to calculate tens, hundreds, thousands in their heads, but are taught to rely on writing methods too early, some children can struggle with mental calculations at a later date.

There is method in their madness

Not formal written methods please. Use a number line and count backwards