Lesson video

Hello, everyone, I'm Mrs.Crane.

And welcome to today's lesson.

In today's lesson, we're going to be subtracting using the column method.

In a moment, I'll run through any equipment that you'll need for today's lesson, so don't worry just yet.

If you can, can you please turn off any notifications on your mobile phone or tablet, or whatever device you're using to access today's lesson.

And then if you can, try and find someone nice and quiet in your home so that you're not going to be disturbed during our lesson today.

When you're ready, let's begin.

Okay then let's run through today's lesson agenda.

So we're going to start off by looking at regrouping and what it means.

Then we're going to have a look at your turn, sorry, for our let's explore , we're going to look at your turn.

Then we're going to look at regrouping, and how we know when we need to.

And then our independent tasks today will be to solve some subtraction equations.

So today, you will need a pencil and some paper, so please pause the video now, try and get those things if you have not gotten them already.

And welcome back.

Let's get started.

So why would we need, and when would we need to use column subtraction? So if I wanted to work out some information, so if I wanted to work out how many more people travelled by coach to the Louvre, we have the Louvre here on the 1st of August.

So let's follow here's my number 4,376.

Than on the 1st of June, 1,845.

How would I do it? I would need to do some subtraction.

I would need to work out the difference between 1,845 and 4,376.

So today we're going to look at a method called the column strategy, the column method to use, to solve different subtraction equations.

Now it's not always the most efficient, but it can often be a really helpful method that we can use to work out the difference or subtraction.

So we're going to make an estimate before we answer our subtraction, why would it be helpful to make an estimate first? Well, it's really helpful because we know that if our answer is nowhere near our estimate, then we've gone wrong somewhere.

So the number 8,839 is going to round up to 9,000.

So I'm going to keep 9,000 in my head.

The number 5,684 is going to also round up to 6,000.

9,000 subtract 3000 is equal to 6,000.

Not I've put them the wrong way around.

9,000 subtract 6,000 is equal to 3000 maybe even.

I've got myself confused.

I had already worked out my answer rather than set the number, so here is my estimate here.

This symbol here means approximately equal to so we can use it to show that our estimate is here and ready to use when we're coming to using the column method.

So we'll keep that up here and I've made my first number.

I've made 8,839 using my place value counters.

There's a zero here to show that it's a one cause this is my ones column.

My face is just popping it out.

So I've also written it here using the formal column written method.

So you can see here I've lined up my thousands, hundreds, tens and ones.

And I'm going to use both my place value counters and my column method to show you today.

So which column do we need to start in? Absolutely we start in our ones column.

I have nine ones that I want to take away four ones.

Can I do that? Absolutely I can and it gives me five ones.

So I'm going to put five in here.

I have three ones and I want to take away eight from that.

Can I take eight? Not ones sorry, three tens.

I don't want to take eight tens away.

Can I do that? I can't, why can't I do that? The number that I'm taking away is greater than the number that I'm taking it away from.

So this bottom number here is greater than the top number here I need to do something.

What do I need to do? Absolutely, I must do some regrouping.

So I'm going to regroup from my hundreds column and I'm going to regroup.

I'm going to take one of the hundreds, I'm going to put it here.

So now I need to regroup that 100.

What am I going to regroup that 100 into? Yeah, I'm going to regroup it into 10 tens because I know it represents 10 tens.

So here I'm left with 700 and I have 10 tens here which would have represented that 100 here.

And my original three tens here.

So now, can I take eight from here? Absolutely I can so I'm going to take eight away from 13.

Which is going to sorry, before I do that, let me show you exactly what it looks like in my column.

So like we just did, we regrouped one of my hundreds.

So there was now seven hundreds for 10 tens.

So I can put that one here so I can see it here in the same way that I did here, okay? So that we have our 13 tens, like we have here 13 tens, and 700 like we have here.

Now I can take away eight from 13, to leave me with my five tens.

And I can put my five here in my tens column.

Now I have seven hundreds and I want to take away six.

Can I do that? I can indeed, it's going to leave me with one.

So I can put one in here and now I have eight thousands and I want to take away five.

Can I do that? Absolutely I can and it leaves me with three thousands.

I can put my three in here.

Now my answer is 3,155.

Is it close to my estimate? Is it near to my estimated answer? Absolutely, it's not too far away from my estimated answer.

Now, if I've got a number that was completely different to that number there, then I'd know that I've gone wrong.

It's really, really helpful especially, when we're looking at regrouping because we can really easily forget to mark them properly.

And then checking against that estimate tells us if we've made an error or not.

So let's have a look at another example.

If you're feeling confident, I'd like you to pause the video now, make your estimate, calculate your answer.

And then, I'd like you to check your answer against your estimate.

Now everybody else, if you're not feeling that confident, that's okay, because we're going to look, firstly, at how we would, if regrouping would occur.

Now I know if I'm taking, the number I'm taking away from has digits and the column that is greater than the digit above it.

So here six is greater than three.

I can not do that without grouping.

So I could already see I'm going to need to regroup in my ones column.

Let's make an estimate so that we know that if we go wrong at all, we'll know.

So 7,700 rounds up to 8,000, 4,400 rounds down to 4,000, 8,000 take away 4,000 it is 4,000.

So my estimate, my approximately equal answer is 4,000.

Now, first thing that I'm going to do is make my number on my place value great again, this column represents the ones.

My face is just halting it.

So I've got 7,773, and I want to take away 4,426.

Again, they're lined up here.

I can clearly see the only column I think I'm going to need to regroup them is my ones.

Is my one's column the digit in the second number, the number I'm taking away from a whole.

My part is greater than the number that was in my whole.

So six, take three we've already decide we can't do that, how are we going to regroup that? Well, we're going to look at tens column.

And we're going to take one of our tens.

And we're going to make it into 10 ones here.

We've still got our remaining three ones here.

Now, can I do 13? Sorry, I was going to show you how it looks here before I get carried away.

So I'm left with six tens.

You can see six, tens here.

So I've got to put that line through here and I've now got 13 ones, as you can see here.

Here are my 13 ones, 13 subtract six.

It's going to leave me with seven, some I'm going to put seven in here.

Now I've got six.

And I would like to take away two.

I know that six and that two represent tens, I'm left with four tens.

Then I have seven hundreds and I want to take away four hundreds.

Can I do that, without regrouping? I can indeed.

It's going to leave me with three hundreds here they are, I'm going to put in my three hundreds here.

I've got 7,000 and I want to take away 4,000.

Can I do that without regrouping? Absolutely, I'm left with 3000.

So my answer is 3,347.

Is it that far away from 4,000? Nope, not too far away from 4,000 at all.

So I know that I haven't gone terribly wrong anyway.

All right then it's nearly time for your let's explore.

And it's going to be your turn today.

So, what I would like you to do, please estimate the answer, check I'm sorry, not check.

You need to actually calculate it first.

Calculate your answer, then check against your estimate.

Your equation today is 7,363, and I'd like you to take away 4,127.

Using that frame remember.

We will need to be regroup in that column.

I know this because, so look really carefully.

Which columns are you going to need to regroup in, Pause the video now to have a go at today's let's explore.

Okay, welcome back.

Let's have a look then our estimate.

So I've rounded 7,300 down to 7,000, 4,100 down to 4,000, 7,000 take away 4,000, leaves me with 3000.

So here's my approximate answer, my estimate.

Now to work out, we need to look really carefully at the columns.

Did you work out which columns you were going to be required to regroup them? And if you did, how did you know? From looking in here I know that I'm going to have to regroup in my ones column.

because I know that seven is greater than three.

I think that should be the only column I need to regroup them.

So let's have a look, my six tens become five tens because I need to regroup one group, one 10, sorry for 10 ones.

So now I have 13 subtract seven, which gives me six.

five subtract two, which gives me three, three subtract one, which gives me two and seven subtract four, which gives me three.

So my answer is 3,236.

All right then let's have a look again at where the regrouping will occur.

What I want you to do, is think about again, how you'll make your estimate.

So if you're feeling confident pause the video now to have a go at this, if you're not feeling so confident, don't worry.

So let's make our estimate 9,200 rounds down to 9,000, 2,900 rounds up to 3,00, 9,000 subtract 3000 gives me 6,000.

So I'm going to put that as my estimate.

I'm going to put it up here so that I know that once I've calculated, I can check back against my estimates.

So let's see I've made the number 9,276.

And then I also made it here in the columns.

Let's see which columns we think we're going to need to regrouping.

No, don't think I well, Nope.

Yes.

Why have I said yes to the hundreds column this time? What's different about my hundreds column to my tens and my ones column? Well, I know that the digit in my hundreds column is greater than the digit I'm subtracting it from.

So I know I'm going to have to regroup here and no I shouldn't need to regroup that.

So let's start off with my six, take five.

Six take away five leaves me with one.

So I can put that into here.

Seven tens take away four tens leaves me with three.

So I can put three in here.

When I'm saying three I know that three really represents three tens, because it is in the tens column.

Two and I want to take away nine.

Can I do that? We've already said, we know we can't.

So we're going to need to take one group of our thousands.

So one of our thousands, and we're going to need to regroup that into 10 hundreds, by doing it like this, so it's going to become 10 hundreds here and you can see here.

I now have 1000 less in my thousands columns.

So let's see how that looked when I write it in.

So I regrouped one group of my thousands to give me eight thousands remaining and it's become 10 hundreds.

There are my 10 hundreds.

I know I can do that because I know there are 10 hundreds in one 1000.

There's also that two here.

Why are there 200 here? Because there was already 200 in my column.

So now can I take nine away from 12? Absolutely, I can.

It's going to leave me with three.

So I can put in my three here.

Can I still do eight to take away two? I can indeed and it leaves me with six.

So we're going to put in 6,000 here.

Then I compare my answer, which is 6,331.

Is it not far away from my estimate? It's not at all, it's quite close to my estimate.

So I know I haven't gone terribly wrong somewhere.

So it's now going to be times for your independent task today.

You're going to become a bit of a detective and solve some subtraction equations.

I'm just going to hide myself so you can see your questions.

So look at these bar models here, I would like you to write these subtraction equation that represents.

Firstly, I'd like you to estimate your answer.

Then you use the columns of subtraction to calculate the missing parts.

Remember check back against your estimate, see if you've gone wrong, or if you've not gone wrong and you've worked out correctly.

And my challenge today is can you work out which columns you're regrouping will need to occur in before you work out, answer to your calculation.

Pause the video now to complete your independent task today.

Don't forget to resume then once you've finish so we can go through the answers together.

Okay, welcome back.

So I'm just going to move myself slightly so that you can see what's going on here.

So what we're going to do then is our first two equations.

So here you can see we've got 8,746 and we want to take away 5,394.

So we've made our rough estimate.

It's given me 4,000.

Now I'm going to work out my calculation.

So six take way four is two, four take away nine I know I can't do it.

So I need to do some regrouping.

My 700 becomes 600 and I have another regrouped hundred as 10 tens, 14, takeaway nine is equal to five.

I know they really represent tens, sorry, because they're in the tens column.

Six, take away three is equal to three and eight takeaway five is equal to three as well.

Is it close to my estimate? Yep it's not too far away from it.

Next we're going to have a look I'm going to move myself again.

And this one here.

So we're lifting now at this equation here, 9,417 take away 2063 my estimate gave me 7,000.

So let's have a look back over here then at our column method to see how we do it.

Seven takeaways three, can I do that? Absolutely and it gives me four.

One takeaway six, can I do that? I can't, I need to do some regrouping.

So I'm going to regroup one of my hundreds to leave me with three hundreds and give me 10 tens.

So I now have 11 tens take away six.

Can I do that? Absolutely, I can.

11 take away six gives me five, three takeaway nothing.

Gives me three.

Don't forget if we're taking away nothing from something zero from something.

When you're doing a number takeaway zero, it gives you the number, not zero.

Sometimes it's really easy to put zero in here and make an error there.

Nine subtract two is equal to seven.

So my answer is 7,354.

Is it close to my estimate? Absolutely it's not too far away from my estimate.

Next we're going to look at the next two again.

I'm going to move my face.

So 7,285 here, 2,327 here sorry.

I've made my estimate and it's 5,000.

Which column do I start in? Absolutely I start in my ones column.

What can you notice about my ones column? I can't take seven away from five without having to regroup.

So I need to regroup one of my tens, which is going to become seven tens or 10 ones.

15 take away seven gives me eight, seven takeaway two, I can do that.

That gives me five, two take away three.

Can I do that? I can't because the number I'm subtracting from is greater than my whole, so I need to regroup my thousand.

So I'm going to take one group of thousands, to leave me with 6,000, to give me 10 hundreds.

So I now have 12 hundreds here and I want to take away three from that, leaves me with nine, 6,000, take away 2000 leaves me with four.

Is that number close to five thousand four thousand nine hundred and fifty eight? Yes, indeed, it is.

And last but not least question four 6,818 subtract 2,793 I made my estimate and it's 4,000.

So I've written it into my column method and I start with my ones, eight subtract three.

Can I do that? Yes I can, it gives me five.

One subtract nine, can I do that? No, I need to do some regrouping.

So I'm going to regroup one of my hundreds to leave me with 700 for 10 tens.

So I now have 11 tens take away nine tens.

I can do that, they cause me two, seven take away seven, I can do that.

And it losing the zero.

It's really important we put that zero there as a placeholder.

Six takeaway two, yes, I can do that.

And it gives me four.

I'm really, really impressed today.

If you'd like to please ask a parent or carer to share today's work, on Twitter by tagging at @Oaknational and using the #LearnwithOak.

Well done today.

Fantastic work, especially when we're looking at regrouping from more than one column, I've been really impressed.

Now don't forget to show off all of that fantastic learning by completing today's quiz.

And hopefully I'll see you again soon for some more math.

Thank you and goodbye.