# Lesson video

In progress...

Hello, my name is Mrs. Behan.

And for this lesson I will be your teacher.

In this lesson, we will learn to add and subtract 1000 from other numbers.

I'm sure you are already fantastic at adding and subtracting two digit and three digit numbers.

Well, in this lesson, we'll start to work with four digit numbers.

Let's look at the Lesson Agenda.

Then we will practise subtracting 1000.

We will represent calculations with manipulatives and at the end of the lesson there will be an independent task for you to have a go at.

I know you'll be keen to find out how you got on.

So I will go through the answers with you.

There are just a few things that you will need for this lesson.

Something to write with, so a pencil or a pen and something to write on.

So grab yourself some paper.

If you don't have those things to hand at the minute, just pause the video here whilst you go and get them.

And remember, try to work somewhere quiet, where you won't be disturbed.

So, here is Anna and here is Junaid.

Anna and Junaid were having a Place Value Battle.

Basically they spin a spinner which showed them four digits.

These are the digits that Anna landed on.

So she got five, one, nine and six from spinning the spinner.

Junaid got seven, two, six and nine from spinning the spinner.

The aim of the game is to create the largest possible number using the digits that you have won.

So can you arrange Anna's digits into the biggest possible number and Junaid's digits into the largest possible number too.

I'll wait here for a moment whilst you have a go.

Okay, so what is the largest possible number that we could have made for Anna? It is 9651.

Our largest number needs to go in the thousands place, because that has the largest value.

All of the other numbers get 10 times smaller as they go to the right.

Each number, 10 times greater as it moves to the left.

So the number of the greatest value is this first one.

So she really needs to use the largest number there, which is nine.

What did you come up with for Junaid? Well, Junaid also had a nine and he has cleverly put it there first.

So his number, read it with me is 9762.

So who is the winner? It is Junaid because 9762 is greater than 9651.

How do we know it's greater? They have the same number of thousands.

So we look to the hundreds and Junaid has one more hundred than Anna does.

Okay, can you count in hundreds with me? 100, 200, 300, 400, 500, 600, 700, 800, 900, ten hundreds, Oh, I mean a thousand.

Well, actually they both mean the same thing.

So ten one hundred is the same as 1000.

If I counted in multiples of a thousand, how do you think this number track might look different? Let's have a look and see 1000, 2000, 3000, 4000 5000, 6000, 7000, 8000, 9000, 10000.

So how does this look different to counting in multiples of 100? Well counting in multiples of 100, you used three digit numbers, but here we have four digit numbers.

Okay, have a look at the question on the screen.

What happens to the ones digit when we add or subtract a multiple of ten? Now you will already know the answer to this, but we are going to prove it.

Option one.

The number of ones does not change or option two, the ones move one place to the left and a zero is puts in the ones place as a placeholder.

Which of those options is correct? Have you decided? Okay then.

Well, let's have a look, let's test it out.

I've used very, very simple numbers.

So I've used two as my ones digit and a multiple of 10.

Well, why not just go with 10? Let's make it very, very easy.

Two plus 10.

Let's show it with deans.

Here's two, I'm adding my multiple of 10.

So here is 10 more.

That together equals 12.

So it's actually option one.

The number of ones did not change when we added 10, nothing happened to our ones here.

So the ones digits stay the same.

I can try it when I subtract a multiple of 10 now.

So I started with 12.

Let's take away 10 and I'm still left with two.

So again, the ones digit has not changed.

Is it any different when we add or subtract a multiple of 100? Well, let's test it out.

Option one, the one stay the same.

So this is what happens to the one digit when we add or subtract a multiple of 100.

The one stay the same, option one or option two, the ones move one place to the left and a zero is put in the ones place as a placeholder.

Which option do you think is right? Let's test it out.

Again, use very simple numbers.

Use two as my ones digit and 100 as a multiple of a hundred.

Why not? There's two deans, at two ones and 100.

What's the total now? That's right, 102.

We no tens, but we have 102 ones.

So the ones have stayed in the same place.

The amount of ones we had has stayed the same, it's not changed.

What about subtraction? 102 subtract that 100, what will we have left? We will have just our two ones left.

So we know it is true that the ones stay the same.

So I wonder what will happen to the ones if we add 1000.

What do you think? Which digits might change? Okay, let's read this word problem together on the screen.

The children at Mr. Slade's school have raised 2141 pounds for charity at their Summer Fair.

Oh, well done children.

Local businessman, Mr. Roy has donated an extra 1000 pounds.

Wow! So how much money will be given to charity in total? You might start having an idea in your mind of what that might look like as a calculation.

So what is that calculation? So here is the number 2141 represented with deans.

Two thousand, one hundred, four tens and one one.

So how can I represent 1000 more than 2141? Any suggestions? Well, why don't we add an extra 1000? We can see now that the calculation we need to do is 2141 plus 1000 is equal to 3141.

So the children and Mr. Slade donated 3141 pounds to the charity.

What is the inverse of adding 1000? Well, the inverse of adding is subtracting.

So let's take off that thousand.

3141 subtract 1000 is equal to 2141.

Have a look here, 3141 subtract 1000 is equal to 2141.

If that's the calculation, what could the context or number story be? So the example given was Mr. Slade and the school children raising money for charity.

But what could we think of for this question here, for this calculation? Pause here whilst you have a little think.

Okay, did you decide on some number stories? Here's one that I came up with.

I said, Daniel's mom bought new bedroom furniture that cost 3141 pounds.

It's very expensive.

Dreamy Night, gave her 1000 pounds discount.

So how much did she pay? So to work that how we would use this calculation.

Wouldn't we? Another number story I came up with was this one.

Annabel ran 3141 metres.

Georgia ran 1000 metres less than Anabel.

How far did Georgia run? Again, to work that out we would use this calculation.

So that's the context or the number story for this calculation.

Let's just have a quick look at what did we say about the digits changing? So is the ones affected when we subtract 1000? The number of one stays the same.

What about the number of tens? Does that change? No, that stays the same.

The number of hundreds, does that change? No, that stays the same.

So when we subtract 1000, only the thousand digit changes.

3000 subtract 1000 is equal to 2000.

So this is Anna.

Anna has a value of 324.

She says that's three hundreds, two tens and four ones.

And you can see how she's represented this using her place Value Counters.

She then says, I am adding 1000.

So I add 1000 to the set.

324 plus 1000 is equal to 1324.

Did any of the other digits change? Not one, only that we had 1000 here.

This is Junaid, and Junaid actually started with 1324.

He says that's one thousand, three hundreds, two tens and four ones.

I am subtracting 1000, so I take 1000 away.

There are zero thousands, but the other digits have not changed.

1324 subtract 1000 is equal to 324.

So we've just lost that 1000.

But all of the other digits stay the same.

Pause here and have a go at calculating these calculations.

So all you need to do is just fill in the missing numbers.

Remember what you've learned about the digits changing.

Okay, then let's have a look.

So 1234 plus 1000 is equal to 2234.

So we didn't change, the hundred tens are the ones we just added one, 1000 to the 1000 we had already over here.

469 plus 1000 becomes 1469.

We've made this three digit number into a four digit number.

Let's subtract now, 6543 subtract 1000 is equal to 5543.

We only took 1000 away from the 6000, which left us with 5000.

The other numbers in the hundreds, tens and ones, places remained unchanged.

1469 subtract 1000.

Nice and easy.

We've taken it into a three digit number now, 469.

So we've just taken off this 1000 here.

Zara has done some calculating, but unfortunately she has made a couple of mistakes.

She thought that 203 plus 1000 is equal to 10203.

She also thought that 7659 subtract 1000 was 6548.

What do you think Zara has done wrong? You might want to pause the video here you want to have a little think.

Okay, well, let's look at this first example up here.

What do you think the mistake is that Zara has made? Well, we've noticed that the hundreds, tens and ones are the same.

We have 203 here, and we can see the hundreds, tens and ones here are the same, which is correct.

Because if I did a thousand, but there is a zero in the thousand place instead of a one.

So she's put a zero there and it should be a one.

So 1203.

So that Zara's mistake for the first one.

And looking at the second example, did you spot Zara's mistake? Well, we know that the thousands digit is correct because we are supposed to be subtracting 1000 from 7000, which leaves 6000.

The hundreds, tens and ones though, should all stay the same if we subtract 1000.

But here, I think she's got a little bit confused because she's decreased each one.

Each of their hundreds, tens and ones by one as well.

Now that you know which digits change and which ones stay the same, you are ready for your independent task.

I'd like you to use an efficient mental strategy to complete the calculations.

Draw a pictorial representation of each calculation.

And there's an extra challenge to think of a word problem, to go with each calculation.

So you need to fill in the missing boxes.

When you've done that, here is a word problem.

Preet scored 2175 points on the first level of her game.

She also got a 1000 point bonus for completing it quickly.

What was her total score for the first level? And here I'd like to think about what's calculation is being represented.

So look at this calculation of the picture here.

And when you've decide on the calculation, write in this box.

When you've decided what this calculation or this picture represents, put the calculation in this box.

When you're ready, come comeback to me and we will look at the answers together.

Okay, then so well done on having a go at your independent task.

Did you find out the missing numbers? 243 plus 1000 is equal to 1243.

We had a missing symbol in this question, 2225 subtract 1000 is equal to 1225.

2114 subtract a thousand is 1114.

So the hundreds, tens, and ones stay the same, but we took off one, 1000 from the 2000.

1000 plus 2114 is equal to 3114.

3315 is equal to 1000 plus 2315.

1345 is equal to 2345 subtract 1000.

So how did you get down with Preet's word problem? Preet's total score was 3175 because she had 2175 points plus 1000 bonus points.

What calculation is being represented here? Well, this one is 1121 plus 1000 being added into the set.

And this one, 4381 plus 1000.