Maths help needed KS2 4 digit column subtraction with zeros!

[23balloons]

My son is in Y3 but is pretty good at Maths and was complaining the work he got was too easy. I mentioned this at parent's evening and the teacher said she would give him harder work. So for the past couple of weeks him and another boy have been bringing home homework with 4 digit addition & subtraction. He hasn't leart how to add & subtract using columns in school but the numbers are so large I told him to use columns and showed him how to do it.

This morning i have come across a problem I cannot remember how to advise on subtraction when there are zeros and you need to borrow? Eg. He has to subtract 1483 from 3002. My column method was working fine until he asked how do you borrow from a zero? I don't want to give the wrong advice and confuse him so are there any teachers or maths gurus out there who can help me with the right advice in this situation?

Many thanks

At school in year 3 they would use a number line to work this out by counting on from the lower number to the higher number in jumps.

Or if you want to do column method you have to borrow from the 3000 into the hundreds column. Making that a 10 (or 100 in relaity). Then borrow from the hundreds to the tens column. Does that make sense? Then carry on as normal.

Doing it in columns, you keep borrowing from the column(s) further to the left if necessary. So you borrow one from the 3 so that it becomes 2 and the first zero becomes 10, then you borrow one from that 10 so that it becomes 9 and the second zero becomes 10, then you borrow one from that 10 so that it also becomes 9 and the 2 becomes 12.

you borrow 1 from the next column, so you've got 10

Not really cece. 2 cannot subtract 3 I cannot borrow from the tens or hundreds if I borrow from the thousands what would the working out be?

They specifically don't teach columns in year 3 as it prevents them learning the principles of numbers.

P&L has it right.
but it is a difficult concept to grasp in only year 3 (and later on tbh!).

Can you try getting him to count on?
eg (not sure i can explain this right written down):
to 1490 is 7 (write it down/remember)
to 1500 is another 10 (17)
to 3000 is 1500 (1517)
plus the last 2 (1519)?

thanks I think I have got it now I borrow from the 3 then from the 10 reducing the hundreds to 9 etc - thanks.

Slightlymad I know they don't like columns in Y3 but the homework he is being given has POS 4a at the bottom so I am assuming it is above Y3 work and therefore columns are the best method. Last week he was being asked to add up to 4 digit numbers and it didn't make sense any other way. i just didn't want to teach him the wrong method.

Thanks for your help.

DTDs are in year 3 and they are confidently doing 3 (and some 4) digit numbers ona a number line (count up on a number line from teh lower number - first the units and then the tens and then the hundreds...then add them all together).

page 6 explains how he should be doing the subtraction.

Finding the difference between the two numbers would be a much better method for this calcultion and Year 6 children would do this mentally so it isn't essential to teach the column method, particularly as is is cumbersome for this particular question.

So...1483+17=1500
1500+1502=3002
Then add the 1502 and 17 to get 1519 and you have your answer.

This is probably how he would have been shown at school.

Yes I would do it

1483 + 7 = 1490
1490 + 10 = 1500
1500 + 500 = 2000
2000 + 1000 = 3000
3000 + 2 = 3002

Then 1000+500+10+7+2 = 1519

That is how it is taught.

I agree for this particular question there are better methods. He doesn't like number lines but could have worked this one out without columns, it is just that I couldn't remember the rules on this kind of subtraction if you were to use columns.

The reason I am teaching him columns is because last week he had to add 2, 4 digit numbers a 3 digit number and a 2 digit number and it was a lot easier to just put them all in a column.

Thanks again for all the advice.

I don't think they introduce columns until yr5/6

I know where you are coming fromo 23 balloons - I have just been through teh same thing in my house.

It is easier for you because that is the way you were taught.

Having taught myself to do it the way that they now teach in school my own mental arithmetic is soooooooo much improved.

My 2 have only ever done it with columns since year 2 (2 digit) and in year 3, 3 and 4 digit for addition and subtraction. They would be confused by the other method.

Don't use the word 'borrow', you are not borrowing you are changing a ten to ten units or 100 to ten tens.