Lesson video

In progress...

Hi mathematicians.

It's me Miss.

Charlton and a Hedwig, who's finally taken off her scarf now, I think she's warm enough maybe.

And we are ready for our final lesson of this unit, with addition and subtraction within 20, very exciting, doing some fantastic learning.

Today we're going to use mathematical models and strategies for subtraction.

We're going to identify subtraction equations in context, and then we're going to consider different solutions to solving mathematical problems. Then you'll do your independent task and your end of lesson quiz.

You're going don't need a pencil and some paper and a number line, but don't worry we'll draw a number line later on in the lesson.

Let's go through our star words, and the star words, subtract and that subject minus partition, make 10.

Well done.

Now we've got that bus again and the bus driver really wants our help.

Bus driver cannot keep track of how many people are coming on and off the bus every day, and really, really need some help.

Do you think we can help this bus driver? I think we can.

We've got an equation to do here.

We've got our story first, then and now, and we're going to figure out how we can solve the problem.

First there were 12 people on the bus then eight people got off the bus, how many people are there now? Well, let's think about what operation we need to do for a start.

First there were 12, and then 8 people got off.

If people are getting off, it means the number on the bus getting smaller, they're decreasing.

We need to do a subtraction equation.

Everyone should mean subtraction.

I wonder how we could do this.

We have learned so many different strategies and so many different ways we could use any of these ones or more to solve this problem.

We could use a tens frame, we could use a partition strategy, we could use a number line or look at it on a bead string.

Let's start off with a number line.

Shall we? We've got the number 12 and we need to subtract eight.

How are we going to do that? I've started off with 12, which means that we must start at the number 12.

And how many jumps do we need to do? 8.

Because 8 people are getting off.

So that's 1, 2, 3, 4, 5, 6, 7, 8, 12, subtract 8 is equal to 4.

Let's try and say that in a full sentence.

12 subtract 8 is equal to 4.

Lovely mathematical reasoning everybody.

We got it right.

12 subtract 8 is equal to 4.

That's not the only way we can solve that equation.

We could also do it through making 10 and partitioning.

What do we need to do first? We need to make 10.

How do we make 10? Well, I know that 12 subtract 2 is equal to 10.

I know that I have to subtract 8 eventually, but if I start off by subtracting 2, then I can get this down to 10, which will help me solve the rest of the equation.

How do I get that 2? Well, I'll use the eight people that were on the bus, I'll make one of them as part of the 2, and the remaining probably 6, because 6 plus 2 is equal to 8.

12 subtract 2 is equal to 10, then I take that 10 and I subtract the remaining amount which is 6.

10 subtract 6 is equal to 4.

So, 12 subtract 8 is equal to 4.

Let's try that to school sentences together.

First we make 10.

So we say 12 subtract 2 is equal to 10.

Well done.

Then I need to subtract the remaining amount, which is 6.

I say 10 subtract 6 is equal to 4.

Well done.

12 subtract 2 is equal to 10, 10 subtract 6 is equal to 4, so 12 subtract 8 is equal to 4.

well done.

And now we can check that on a tens frame as well.

I've got 12 here, I've got a pop a whole 10, can you see the whole frame is filled in, and there are two ones, 10, 11, 12.

All of them showing me that we've got a whole of 12, now I need to subtract.

How many of my subtracting? 8.

1, 2, 3, 4, 5, 6, 7, 8.

I've subtracted 8, and how many are left? How many dots are there still on the tens frame? There are 4.

So we got it right? 12 subtract 8 is equal to 4.

Now, it's your turn to have a gap, but we're going to have a little competition.

We're going to have a race.

What we need is to get some paper, and then put Hedwig over here because I don't want to draw when I'm making my number line.

The first thing that we're going to do, is demonstrate this equation on a number line.

We need to draw a number line.

Let me make it big so you can see.

The first thing we need to do, is align all the way across.

Everyone go all the way across.

Just like that.

It doesn't matter if it's not perfect, now at this end, we know that we have zero, and at this end we have 20 because we're going for numbers up to 20.

Now to help me put the rest of the numbers on, I know that half way between these two, is 10.

I'll put approximately here and I'll say that's 10.

And then we can start to put the other numbers on.

I hope you are doing this at the same time.

Let's see who gets that first.

I know that 5 is in the middle, so 5 can go there, and now I could put the rest of my numbers on.

0, 1, 2, 3, 4, 5, I've got up there, and now I need to do 6, 7, 8, 9, 10.

I've got my numbers up to 10.

How are you doing? Did yours look similar? Now I can carry on.

10 and 20.

I know that half way through those about 15, so that will help me put the rest on, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and spelled it wrong then 20.

There's my number line.

Have you got yours as well? Hopefully.

Right now, let's get ready to count.

My equation says 16, subtract 9 and it says it equals 7, but let's double check on our number line.

Shall we? Where do we need to stop? I hope you're doing this at the same time.

Where do I start? I start off with the first number.

First it is you do it.

Did you circle 16 like me? I put my circle on 16, and how many jumps backwards do I need to do? It's takeaway.

I need to go towards the 0 because the numbers are getting smaller, so I need to do 9 jumps.

I'll show you as well.

Are you ready? 1, 2, 3, 4, 5, 6, 7, 8, 9.

What did you end up on? Did you do the same as me? I ended up at the number 7.

16, subtract 9 is equal to 7.

That's one way of doing it.

Should we just double check that? 16 subtract 1, 2, 3, 4, 5, 6, 7, 8, 9 look, we ended up at 7.

We did do that right, but we can also do it another way.

Are you ready? You're going to have another competition here and see who gets there first.

This time, we're going to make 10.

Everyone show me make 10.

I had to put my pen down there.

In order to make 10, we need to draw a partition model like this.

Ready? Everyone's going to draw a box and then we need to do it with the other one's coming off because this is the number that we want to partition and we're going to break it up, partition it into two different parts to help us make 10.

Everyone should have something that looks like that.

Yours might be neater than mine.

Right.

Let's see.

We need the number 16 and we need to make 10 first.

How do I make 10? 16 subtract, how do we make 10? 16, subtract 6 is equal to 10 because 16 has got 6 ones and 6 has got 6 ones.

Where do I get that from? Well, I got it from the number 9.

Everybody put the number 9 into your part.

What will the remaining two numbers be? I know that I needed a 6 to make that number bond to 10 so finish yours and I'll do mine as well.

Did you get the same as me? I know that we were partitioning the number 9, we needed a 6 to make 10, the remaining amount is 3 because 6 plus 3 is equal to 9.

Make sure yours looks like mine.

Don't worry if you didn't get it right.

Okay, let's check on a screen.

Shall we? 6 and 3.

6 plus 3 is equal to 9.

16, subtract 6 is equal to 10, 10 subtract the remaining 3 is equal to 7.

16 subtract 9 is equal to 7.

Let's say that as a full sentence.

Shall we? 16 subtract 9 is equal to 7.

Lovely.

Well done.

Let's check it on the tens frame as well.

I've got 16, I've got 10, 11, 12, 13, 14, 15, 16, and I need to subtract 9.

Let's count them off together.

1, 2, 3, 4, 5, 6, 7, 8, 9.

How many are left? 1, 2, 3, 4, 5, 6, 7.

We got it.

Correct.

It's always a really good job to double check on a tens frame or a number line as well.

Now it is your turn to do that.

You can use any strategy you like to complete the following equations.

You can use a tens frame, the partition model, the number line, or bead string, or you might have another strategy as well that you know, you can choose any of these equations and your favourite strategy to try and solve it.

My challenge to you is to see if you can use all the different strategies for a different equation.

When you've completed them, come back and we'll check through together.

How did everybody get on? Let's see.

16 subtract 9 is equal to 7, 14, subtract 7 is equal to 7, 12 subtract 9 is 3, 17 takeaway 8 is 9, 13 takeaway 9 is 4, 15 takeaway 6 is 9, 18 takeaway 9 is 9, 15 takeaway 7 is 8, and 14 takeaway 9 is 5.

But what I'm interested in is how many different ways did you choose to solve it? Put your hand up, give me a wave.

If you used your number line to count back.

Give me a wave if use your number line for any of them.

Really well done.

Give me a wave, if you drew a bead string.

Give me a wave if you challenged yourself and you made 10 and partitioned the ones.

Well done mathematicians, and who double checked it on a tens frame by drawing dots.

Give me a wave if you did that.

Hopefully, you've had a really great time exploring all of those different strategies.

You have done fabulously today.

Should we wake Hedwig up? She's still sitting over here.

I didn't not call when I was doing my work.

Right Hedwig, we had a lovely time exploring.

We had a bit of a competition to see who could get the answers best.

We needed to identify the different equations that we were doing, and then we explored by choosing different methods.

We found that we could do the same equation, but we could represent it in lots of different ways, and some of us found out what our favourite strategy was.

I think my favourite strategy, what I do like doing the jumps on a number line.

I do like doing that, but I also really like challenging myself with the partition method 'cause I find it really tricky.

Hedwig, do you think you understood what we were doing this lesson? You have been absolutely incredible mathematicians.

Really well done.

I've loved learning with you.

You can go and do your quiz and I'll see you again very soon.

Bye bye.