Lesson video

Hi.

My name's Ms. Robson.

In this lesson, we are going to be looking at how subtraction equations can link to problem solving contexts.

We're going to start by looking at some subtraction and problem solving scenarios, before completing a talk task, then you're going to go on to complete your independent task and finally complete the quiz.

For this lesson, you will need a pencil, some paper, and some objects for counting, preferably in two different colours.

Pause the video here to collect the items that you need, and when you're ready, press play.

We're going to start with our number bond practise.

Today, we're looking at numbers one to eight, and you can see it's beads across the screen and some equations next to them with lots and lots of missing parts.

So on the left-hand side of the equation, we have the part that represents the red beads.

So I have eight plus equals eight.

Then on the right-hand side of the equation, you have the part that represents the yellow beads.

So if I look three equations down, I can see plus two, and I can see two yellow beads is equal to eight.

Pause the video here to try and fill in the missing numbers of the equations, and when you're ready, press play.

Let's have a look at the answers together.

Eight plus zero equals eight.

Can you read them with me? Seven plus one equals eight, six plus two equals eight, five plus three equals eight, four plus four equals eight, three plus five equals eight, two plus six equals eight, one plus seven equals eight and zero plus eight equals eight.

Fantastic.

Now that our brains are nice and warm, let's have a look at our problem solving activity for today.

Jenay has made seven bracelets altogether.

I remember in a previous lesson, if you joined me for that one, we've talked about Jenay before.

This time, Jenay has made seven bracelets altogether.

Three of the bracelets are red and the rest are blue.

Pause the video here to get your manipulators ready to join in with me.

You'll need seven things.

So, I'm going to use cubes.

One, two, three, four, five, six, seven.

Here are on my seven cubes.

And I know that three of the bracelets are red.

The rest are blue.

So I know how many red there are, but I don't know how many blue there are.

I'm going to complete a subtraction equation to figure this out.

So I have seven altogether and I know that three are red.

One, two, three, therefore the rest must be blue.

So I've taken away my three, as one part, and the other part is how many blue bracelets there are.

Let's have a look at that in the part whole model.

So at the top, I can see the three cubes that represent the red bracelets.

And at the bottom, I can see the cubes that represent the blue bracelets.

They're not in different colours this time, because we just started with the whole and shared them into the two parts of the part whole model.

Let's try writing an equation to represent what we've done there.

So we started with seven.

We started with the whole, seven take away red bracelets.

So seven take away three is equal to four.

Seven, the whole, take away three is equal to four.

Can you try describing to me what the different parts of that equation stand for? What the different numbers in that equation represent? So there's the number seven, the number three and the number four.

Pause the video here to have a go at explaining what the different parts of the equation mean.

I know that the seven is how many bracelets she made altogether.

Three represents how many bracelets are red and four represents how many bracelets are blue.

So, four was the missing bit that we didn't know, the part of the information that we weren't sure of.

For your talk task, you're going to tell some math stories, just like the one about Jenay and her bracelets, about the pictures that you can see on the screen.

So I'm going to start by looking at the fish.

Now, altogether, there are nine fish.

When we do subtraction equations, we start with the whole because we know how many there are altogether, but some leave, some disappear, or we're trying to find a missing value.

So we're going to start with nine and nine is the whole.

I'm going to grab nine things.

One, two, three, four, five, six, seven, eight, nine.

Here are my nine cubes.

I know that there are five goldfish, one, two, three, four, five goldfish, and the rest are blue.

So nine take away the five goldfish gives me the value of how many blue fish there are.

One, two, three, four.

Can you count on the picture to check, to see if I'm right? So my maths story would be, all together in the tank, there were nine fish, five of them were goldfish.

How many of them were blue fish? Four were blue fish.

Let's check that as a, let's check that on our number line.

So here, we're going to start at nine and we're going to hop back five times.

Okay, so count with me.

One, two, three, four, five.

So the remaining part should be four.

Nine take away five is equal to four.

Let's write that as an equation, nine take away five is equal to four.

Let's have a think about some of the other math stories that you could tell.

You could talk about, how many fish in the tank are big.

So, altogether, there were nine fish in the tank.

There are five big fish.

How many fish were small? Or you could talk about how many are facing right and how many are facing left.

You could talk about how many fish are swimming at the top of the tank and how many are swimming at the bottom.

There are lots of different parts that you could make from this picture.

So you need to get your nine things, a piece of paper to practise writing your equations on and a pencil.

And you could also draw a part whole model to move your objects around and if you think that would help you.

Pause the video here to complete your talk task, telling as many math stories as you can come up with and when you're finished, press play.

So we're going to have a look at a few more subtraction, maths stories together.

I can see some sheep, some are inside a field, some are out, some are big, some are small, some are facing left and some are facing right.

I might actually start with that.

So there are seven sheep in the field altogether.

Let me get my manipulatives to represent that.

Here is seven, one, two, three, four, five, six, seven.

There are seven sheep together.

Let me get my mouse on the number seven, and four of them are facing left.

So how many are facing right? I'm going to complete a subtraction equation to figure that out.

So seven altogether, with four facing right, how many, four facing left, sorry.

How many are facing right? Let's subtract.

So I'm taking away four, one, two, three, four.

And I'm also going to check that on my number line.

So I'm going to start at seven and bounce back four.

Ready? One, two, three, four.

Seven take away four is equal to three.

My parts are, four and three.

I can check my equation by adding them back together again.

So four was a part, three is a part, the whole is seven.

Seven sheep in the field, four looking left, three looking right.

Let's try one more equation.

I'm going to look at the baby sheep.

Now when I say baby, I mean very little, 'cause there are some different sizes sheep here, but I'm going to look at this one here.

So it'd be a lamb and two and three over here.

So three lambs in the field.

How many sheep are there that are older? So again, we have seven to start with.

We start with the whole for a subtraction equation.

Seven is the whole and three are lambs.

How many are adult sheep? So I have seven altogether, take away three.

Let me start at seven on the number line and bounce back three, can you count with me? One, two, three.

Seven, take away three is equal to four.

Let's write that as an equation.

Can you say it with me? Seven, take away three is equal to four.

Fantastic.

So I've told a math story.

I've used my manipulatives to help me, but I've also used the number line to count back.

For your independent task, you're going to have a go at coming up with some subtraction math stories.

Now, if you remember this picture from one of our previous lessons, there's something special about it.

If you don't know, let me tell you.

One of the owls is asleep.

That's one of my favourite math stories that you can tell with this picture.

There are eight owls altogether.

So here are my eight owls.

There are eight owls altogether.

Here on my eight cubes to represent my eight owls.

One of the owls is sleeping.

How many of the owls are awake? So seven take away one.

Oh, sorry.

so eight, take.

Here are my eight cubes to represent the eight owls being very quiet because I don't want to wake the owl up.

Eight owls altogether, and one is asleep.

How many are awake? That's going to be my math story.

Eight owls altogether, and one was asleep.

So this many owls were awake.

One, two, three, four, five, six, seven.

One less than eight is seven.

Eight, take away one is equal to seven.

I could check that on a number line as well if I need.

Your task is going to be to come up with lots of different math stories and have a go at writing the takeaway equations that accompany those math stories.

So just like we were doing in our sheep subtraction problems, we were counting, making up a story and then subtracting a part from the whole, writing the equation and using the part whole model if we needed to help us too.

Pause the video here, to complete your task.

Remember, you're trying to tell as many creative stories about the owls as you can.

I'm recording the subtraction equations that go alongside.

When you're finished, press play.

Let me show you some of my favourite math stories.

I'm just going to show you two of my favourite math stories.

The first one is about where the owls are because one of these trees is a special tree.

This tree over here, is a special tree.

It's a different tree to the rest of the trees.

It's the biggest tree.

So first there were eight owls.

Then, this one owl decided to rest in the big tree.

How many owls were not in the big tree? Eight owls altogether, one, two, three, four, five, six, seven, eight owls altogether.

And one of them decided to sit in the big, most comfortable tree.

So I'm going to take away that one owl.

How many owls were left? One, two, three, four, five, six, seven.

One less than eight is seven.

I've written the equation for that too.

The whole, eight subtract one of the parts, one, is equal to the other part, seven.

Eight take away one is equal to seven.

Do you know, that's a bit similar to the math story I told you earlier, about the sleepy owl, isn't it? It uses the same numbers, but I've talked about a different story to explain the different parts.

The next story I'm going to tell you is about what the owls are doing.

I can see that there are eight owls altogether and three of them are flying.

Here is my whole.

Here's eight and three are flying.

One, two, three.

So I'm going to take that part away.

to find out what my remaining part is.

Three is a part and five is a part.

Eight take away three is equal to five.

Three and five are equal to eight.

Remember, I can add them back together again, to check that my equation works.

Here, I've written the equation slightly differently.

I've started with the parts of five to say five owls are sitting on a tree.

Five is equal to eight, take away three.

So five is equal to eight take away three.

When I have eight and I take away three I'm left with five.

This equation is written in a slightly different way because I haven't put the whole first, but, and I've changed where the equal sign is, but, when you read it from left to right, it still demonstrates my math story.

Do you know, I wish that you could show me your math stories.

But actually you could, if you'd like to.

Why not share your math stories with us? If you'd like to, please ask your parent or carer to share your work on Instagram, Facebook, or Twitter by tagging @OakNational and using LearnwithOak.

I'd love to see all of the amazing math stories that you came up with about the owls.

Don't forget to go and complete the quiz.

Thank you so much for joining me today.

I've learned so much and I hope that you have too.

I'll see you next time.