Lesson video

Hello there mathematicians, it's miss Charlton here and Hedwig my wonderful tool partner.

I hope you have your tool partner ready as well because today we are starting a new unit.

I'm very excited.

Hedwig is also excited today because she went to the countryside recently and she got to explore in her natural habitat and I think that she chatted to some other owls while she was there.

So she is feeling very happy.

I had a countryside accident with a fence.

A sharp of a fence hurt my hand.

So if you see my sore hand in the video that's what happened to me.

But I think I'm very brave.

Hedwig, was I brave? Oh she is nodding.

Isn't she nice too? Anywhere let's get started with our Maths.

Let's find out what we going to do today.

So today we are going to use number bonds when subtracting.

We are going to use the whole part model for subtraction and then we going to use that to predict the answers of the subtraction calculations.

Then you will do an independent task and your end of lesson quiz.

Today you going to need a pencil, some paper and a part, whole model which you can just draw on a piece of paper.

It doesn't have to be perfect, or you can use your resources.

Lets get our brains warmed up.

Um, lets have a think.

We are talking about strategies today.

So which strategy would you use for the following addition equations? Have a little think.

Um, six plus two what could we do? Could we make 10? Would we just count on? Would we use number bonds? Have a little think.

Look at these equations.

Lets see now we won't go through all of them, but let's pick some out shall we? Now I can see that six plus two well there is only two once so there is not much really that we have to add on there so we could just count on.

Six, seven, eight.

That's it, isn't it? What about the one with ooh what about seven plus five? Now there is more ones to count there, aren't there? And if we do lots of jumps on a number line, it does more chance that we might get it wrong.

So what we could do there, oh well I know that seven plus three is equal to 10.

Oh, I've made 10.

Seven plus three is equal to 10.

That's my three but I need to add five so I just need to add two more.

Seven plus three is equal to 10.

10 plus two is equal to 10 plus two is equal to 12, well done.

So seven plus five is equal to 12.

Now we will go through the rest let's move on with our lesson.

Right, we have got a number bond here and the whole is six and the parts are two and four.

Now the key things we going to use today is the phrase, if I know, then I know.

Can you say that? well done.

If I know, then I know.

I'm going to tell Hedwig that so she remembers.

Wake up Hedwig.

If I know, then I know.

She's about to sleep again.

So we going to use that throughout today's lesson.

we lets not go with the number bond here we got the whole is six and the parts is two and four.

What we can do is we can write equations based on that number bond.

We know that the whole is six, that's the biggest part the main part of the number bond.

So lets put that whole in both these equations.

The whole is six and the parts are two and four.

Two plus four is equal to six.

Can you say that? Two plus four is equal to six.

Well done.

So there is one of my addition equations but the trick is its a bit like magic.

We can write another addition equation to represent that number bond.

Are you ready? If I know that two plus four is equal to six then I know that four plus two is equal to six.

They are exactly the same parts, two and four but you can represent them in the other way.

If I know that two plus four is equal to six then I know that four plus two is equal to six.

Your turn.

Really great, well done use of if I know, then I know.

What about this one then? Let's have a look.

What's the whole? The whole is, shout at me, shout it really loudly.

well done.

The whole is seven and the parts are three and four.

The whole is seven, the parts are three and four.

Good.

So we know that the whole, the biggest part is seven, and the parts are three and four.

So let's put the knowledge into these equations.

Three plus four is equal to seven.

If I know three plus four is equal to seven, then I know that four plus three is equal to seven.

can you see that pattern there? The same parts, the same whole, but they're represented in different ways.

It's just like magic.

Let's move on.

And have it like a so if I know now that the whole is seven, I need to know the parts.

Not only can we do addition equations, we can also do subtractions equations.

Can everyone show me subtraction hand? Like that, or you can do it with one.

Well done.

So subtraction or take-away or minus.

Let's have a look at how we might do that.

So on this bond the whole is seven and the parts are two and five.

Two and five and the whole is seven.

So for an addition equation, I could do, you're going to do it.

Are you ready? You going to pause the video and I would like you to write out an addition equation that you could do to represent that number bond.

The whole is seven, the parts are two and five.

You got? how did everybody get on? Let's check it together.

The whole is seven, the parts are two and five.

So you could've done five plus two is equal to seven.

You might also have written two plus five is equal to seven.

If you've seen the relationship between the two.

So now how do we do the subtraction equation? Subtraction always starts with the biggest number.

That's the most important thing.

I'd like you to tell someone in your house or your tool partner, subtraction always starts with the biggest number.

I'm going to tell Hedwig.

Subtraction always starts with the biggest number.

Did you share that as well? Lets say it together.

Subtraction always starts with the biggest number.

Welldone.

so which is the biggest number here? The whole.

The whole is seven.

So my subtraction equation must begin with the whole.

So let's put that seven in there and then just like with the addition equations we can use either of these parts to subtract.

Seven subtract five is equal to two.

Look it's exactly the same part.

The whole is the same, the part is the same but we've represented it differently.

Five plus two is equal to seven, seven subtract five is equal to two.

You're just choosing those numbers from that number bond.

What about this one then? Hmm, this looks a bit trickier.

The whole is seven, the parts are two and five.

The whole is.

The parts are 12 and five.

Well, if I know that two plus five is equal to seven, then I know that 12 plus 5 must be equal to have a little think can you see what's the same and what's different? Pause the video now and see if you can figure out what the whole might be.

And then we'll come back and check together.

How did everybody get on? Let's have a look.

The whole is seven, the parts are two and five.

And here, the whole is and the parts are 12 and five.

The difference is that the second number bond has a 10 with it.

Instead of the number two, its the number 12.

So the difference there is 10.

So the difference in the whole must be 10 as well.

If I know that two plus five is equal to seven, then I know that 12 plus five is equal to 17.

You can use if I know, then I know to solve more complicated equations.

What about this one then? If I know that three plus two is equal to five.

The whole is five, the parts are three and two.

Then how can I find the missing part now? Ooh, well I can see that the whole is 15, not five, 15.

The parts are two and well its the same part two, so what must the missing part be? What's the difference there? The difference is a 10.

add the three to the missing part must be 13.

Instead of it being three, it's 13 because we need a 10 to the 15.

If I know that three plus two is equal to five, then I know that 13 plus two is equal to 15.

It's like magic, isn't it? We have gone so well so far I think we need a bit of a celebration.

Shall we do a roller coaster clap Are you ready? Really good.

Now it's time for your Ooh task.

Can you see that we brought some number bonds here, and made some equations with some missing boxes.

Your job is to fill in those missing boxes.

So the first one has been done for you.

The whole is seven, the parts are three and four.

Three plus four is equal to everyone shout at me, seven.

Good.

You can see that's the whole.

Three plus four is equal to seven.

Four plus is equal to seven.

Then you can do your subtraction equation, you just use the numbers in the number bond.

What do we need to remember about our subtraction equations? Everyone tell me, tell it to your partner.

Subtraction equation always begins with the biggest number.

Welldone.

Right,go on and have a go with that and then come back and we'll check the answers together.

How did everybody get on? Let's check.

To the first number bond we have the whole is seven, the parts are three and four.

Three plus four equals seven.

Then four plus three is equal to seven.

If I know that seven subtract three is equal to four, then I know that seven subtract four is equal to three.

Then the other number bond, did you spot the pattern here? I did a little trick.

The whole with marks the same but we just see we didn't have the 10.

So the whole with 17, the parts are 13 and four.

17 is equal to 13 plus four.

17 is equal to four plus 13.

13 is equal to 17 subtract four and four is equal to 17 subtract three.

Those ones were really tricky, because we wrote the equations in the other way.

We just spun it around and that's what you can do with subtraction equations and addition equations.

You can just move them around.

You did a fantastic job today at the Math it was really really tricky she makes fun to help people we did.

Come on Hedwig, I know you did help in the lesson but you've been snoozing a bit as well.

Right.

Well we needed to use a whole, part model a lot today.

What did we use a whole part model for, everybody? Um, well it was to make sure that we can identify the whole and the part, and then we use those whole and parts to be able to write addition equations and subtraction equations.

So if we knew what the addition equation was, we would also be able to know what the subtraction equation would be.

We used a strategy, if I know, then I know.

If I know one equation, then I know another equation using the same parts in that bond.

Do you understand Hedwig? Hopefully you enjoyed that Maths session just as much as I myself and Hedwig did.

Now you can go and complete the quiz and I'll see you again very soon.

Well done everybody!Bye Bye.