Lesson video

Hi, everyone.

I'm Ms. Brinkworth, I'm going to be going through this math lesson with you today.

Let's look at the learning objective to begin with.

So, we've got adding two 3-digit numbers and this is not going to require any regrouping.

What that means is that we can just add each column and it doesn't need regrouping into the next place value column.

All of it will become clear as we go through.

Let's have a look then at our agenda.

So, what we're going to be starting is just recapping those mental strategies that you already know for adding numbers together.

We are then going to have a look at some dienes and how we can use those to add 3-digit numbers and then move on to visualising that.

So, that will help us move on to mentally adding 3-digit numbers together.

It's not as hard as it sounds, I promise.

And then, you'll have your chance for your independent work where you'll have as much time as you need to practise your new learned skills.

And then the exit quiz at the end will give you a chance to see how well that learnings gone in.

Okay, so for today's lesson, pen or pencil and paper.

And if you could also ask a parent or carer to help you find online dienes and help you use them throughout this lesson.

That would be really useful.

So, pause the video here and take as long as you need to find that equipment.

Well, done! Let's get started.

So, here's a little warm-up for you.

You've got some two digit numbers which you need to add or subtract.

In fact, all you need to do, really, is have a think about the fact that the bottom of the page, how those can help you.

So, what's going to appear is some lines from the four boxes at the bottom to all of those addition and subtraction questions.

So, which of those calculations are going to help you solve which of those? For example, five add two is seven.

That will help me when I'm doing 52 add 23.

So, just have a think about where those lines are going to appear to match the calculation, sorry, to match the known number fact, to help you solve the calculation.

Right.

Let's have a look.

So, for five add two is seven we said it could help with this one.

Some lines are going to appear.

They're not going to match to all of them.

It would've just been lines everywhere but, here's just a few to show you that what you can do is use what you already know to help you when you're adding or subtracting much larger numbers.

Which is what we're going to be doing in today's lesson.

So, you all know that five add two is seven.

So, you can use that to help you add that 52 add 23 because, they've both got the five and the two in the tens columns.

So, you can use that fact to help you with that question.

And that number fact can also help you with this question here and this question here.

And this question here! Okay, so.

Lots of questions there that can be helped with that one number fact.

Then, if we move on.

What about eight take away six is two? Well, that can help us here and here.

Four add three equals seven can help us here and here.

And six take away four equals two can help us here and here.

So, we can use the facts that you already know to help you when moving on to larger numbers in today's lesson.

So, let's have a look at what we mean.

Here's a word problem.

Let's have a look through it together.

On Friday, the tour guide showed the Tower of London to 216 visitors.

On Saturday she showed it to 123 more visitors.

How many visitors did she show the Tower to on Saturday? Right.

What type of question is being asked here? Well, we can use a bar model to help us.

What would the bar model for this question look like? So, we know how many visitors she showed the Tower to on Friday.

And then it says on Saturday, she showed it to 123 more.

So, our bar model would look something like this.

On Friday there was 126, showed it to 123 more.

So, what is our unknown is that bit at the bottom, we need to add those two numbers together to get there.

Okay, how do we do it then? Well, we can use our online dienes to help us.

So, if you were able to locate some online dienes with your parents or carer, please have a go at creating this question with your online dienes now.

You can pause the video for as long as you need to just get that question up.

So, you can see, the great thing about dienes, and it becomes really clear what we need to add in each place value column.

So, we look at our big blue square that you can see on my screen that they are our hundreds.

So, I've actually got mine the other way around than it appears in the question, but it doesn't matter, because we know that we can add values in either order.

It doesn't matter.

So, I've got 123 in my dienes added to 216.

And you can see that those big blue squares, which represent 100.

I've got, one, two, three of them So, when I add them together, I'm going to have three hundreds.

So, in my hundreds column, I'm going to have three.

The green sticks are my tens and I can see that in total, I've got one, two, three of those, as well.

So, I'm going to have three tens.

I'm going to have three in my tens column.

When is comes to adding my ones, I've got quite a lot of them.

So, let me see.

I've got six and I've got three.

So, three add six.

Three add six.

That's nine! So, let me get all my dienes together, and that can help me with my answer.

Now, these are great, but they can take quite a long time.

And actually, for this question, I would be able to do it in my head, but I might want to visualise those dienes in my head when I'm doing it.

I might what to think, when I'm adding my hundreds about those big blue squares that represent the hundred.

I might want to think about those green strips that represent ten, and the little yellow cubes that represent one.

Because I can do all of those calculations in my head, I know what one add two is, to get my hundreds.

I know what two add one is to get my tens.

And I know what three add six is to get my ones.

So, I can do all of that in my head, the dienes are a really good way of visualising it.

Seeing it in your head as you do it.

Okay, here's some more dienes then.

What do you think my question is? Pause the video here and work out what the question is.

Have you been able to see it? So, these dienes look slightly different.

We've got different colours.

It doesn't matter.

They represent exactly the same thing.

So, here's my part-whole model.

One of them is 124 and the other is 215.

Willfully, you could read the dienes carefully and see that that's what I was adding together here.

So, like I say, we can get all our dienes together and then we can add them.

Count how much we've got.

Right.

We've got three in our hundreds now.

And we've got three in our tens.

And we've got nine in our ones But actually, you can do that in your head.

You know what one add two is.

You know what five add four is.

So, you can take each place value column, your hundreds, your tens and your ones, and add them all separately, and then put them together.

Okay, your turn then.

Pause the video here.

I've given you the dienes.

Have a go at answering this question.

Let's see how you got on.

So, the dienes are there, but let's see if we can do it in our heads.

So, we start with our hundreds.

We've got two add one.

Two add one is three.

If we look at our tens, this is quite an interesting question because only one of our number has got any tens, and there's just three tens there.

We can see it in 134.

So, our tens must be three because zero add three is three.

And then we need to add together our ones.

Four add four.

I'm sure you all know what four add four is.

And well done, if you got that answer of 338.

Okay, so let's have a think about doing this without the dienes then.

What we are doing today, our success criteria, is that we are partitioning both numbers, and then adding each of those place value columns separately.

So, we are starting with our hundreds.

We've got five add three.

500 add 300 is 800.

I've then got my tens.

70 add 10 is 80, and I know that because I know that seven add one is eight.

So, I need my ones.

Two add two is four.

And when I put those numbers back together for 884 I've got the total answer.

Your turn.

Have a go without the dienes this time and just think about adding the hundreds, then the tens, then the ones, and making sure you've got them all together for your final answer.

How did you get on? Hopefully, you were able to do this working out in your head, but let me show you sort of what it would look like if we could look inside your head and see what you did.

Two add six is eight.

Eight hundreds.

Four add five is nine or 90 for 40 add 50.

And then we've got one add three, three add one is four.

So, your final answer, let's see how well you got on, is 894.

Really, really well done if you got that.

Especially if you could do it all in your head.

Okay, time to pause the video and take as long as you need on those independent tasks.

Come back when you're ready for your answers.

Let's see how you got on.

Please don't worry if you got some questions wrong.

Please carry on with the video right to the end and just have a think about how you'll make sure you'll get them right next time.

Okay, so we've got some question to answer here.

I'm really hoping you were able to do these in your head.

They didn't require any regrouping.

That meant you can just add to each column.

So, I'm really hoping you were able to do them in your head.

So, here are the answers.

I'm not going to go through them in lots and lots of detail.

But really, really well done if you were able to get those answers.

Especially the ones where it's a little bit confusing because you've got the full number that you're looking for before the equal sign.

What's really important to remember is that equal sign just means that both sides of the equation must be equal.

So, if you look at that last question, for example, the right answer is 889, because we've got 700 and 189.

What is the same? What number is the same as 700 and 189? Well, we must add those numbers together to find what it is that's equal to those.

So, really well done if you could get all those answers right.

What about the challenge then? Add two 3-digit numbers together to get 999.

Now there are lots and lots of different ways of doing this and it's a really good, fun mental activity to see how many different ones you can find.

I bet some of you managed to find absolutely loads! And that would be a really good thing to share, when we get to the end of the lesson.

I'll show you how you can share this with us.

So, here's a few that I found, and I found just some quite straightforward, quite boring ones.

So, I thought about nine being three add six so 333 add 666.

And then, and then along with the same thing really.

300 add 699.

And then for the last one, I just took 100 away to give me 899.

So, put the 100 back on.

Well done if you were able to find some of those.

Okay, which one of these do you think would be the odd one out? Okay.

The odd one out here is this question.

Well done if you could see that.

Why is it the odd one out? Well, because we need to regroup.

One of the numbers that we add together in those columns equals to more than 10.

When that happens, we need to move into the next place value column.

So, if you can see here, we've got five add nine is 14.

So, then we carry on in the same way.

We do 70 add 10 is 80.

400 add 100 is 500.

And well done if you could see that the answer was 594.

Okay, so if you would like to share some of your answers with us, especially from this challenge of Part A, that would be amazing.

Please ask a parent or carer to help share your work.

On Twitter it's tagging @OakNational and #LearnwithOak.

And before you go, please have a go at completing the knowledge quiz to see how well today's learning went in! Some fantastic work today everybody.

Really, really well done.

Bye, bye!.