Lesson video

Hello there, everyone.

My name's Miss Brinkworth.

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

Let's look at our learning objective.

So what we're going to be doing is we're going to be understanding that area is a measure of surface and it can be measured in square units.

So that might sound quite complicated.

We're going to go through it together, I assure you.

So we've got quite a simple lesson agenda today, because we are going to be calculating area, and then there's going to be your independent task.

So we're going to talk together, in quite a lot of depth, about what area is and how we calculate it.

You're going to pull in quite a lot of your knowledge that you already have in terms of times tables and arrays.

They're going to really help you.

And then it's going to be a chance for you to have a go on your own.

So you will need a pencil, a ruler, and some paper.

If you can't find a ruler at home please don't worry too much, you're going to be fine without one, but pause the video here and make sure you do have a pencil and some paper.

Welcome back.

Hopefully you've got all of your equipment ready.

Okay, so what is area? How could we represent a rectangle that measures three units by two units? So if we remember that area is the surface of a 2D shape, the space that it takes up.

We know that if we compare that to perimeter, perimeter is just the outside of it, the length of all the sides added together.

Surface is different.

It's a 2D space.

So it's not just a point from one point to another, it's the space that it takes up.

If I think about the area of my notebook, it's all the space that it takes up.

If you think about having some 2D shapes like squares, circles, rectangles, hexagons, and you coloured them in, everything that you coloured would be the area of that shape.

So how would we represent a rectangle that's three units by two units? So we could think of it like this, where I've used three across the top and two down the side, and I've made a shape which is a rectangle.

But that looks just like our arrays, doesn't it? Arrays help us with our times tables.

Well, what have rectangles and area got to do with multiplication? Well, if we look at this rectangle that we've made here, with these three dots across the top and two down the side, what we could do to work out that area, how many dots are being used, we can do three times two.

That's what that array shows us, and that's how multiplication helps us with our area.

Here is a similar array, but this time we've got two times three.

We know that that gives us the same product, which is six.

So this rectangle also has an area of six.

So this is how multiplication helps us.

We can multiply one side by another to work out the area of a rectangle.

But what do we measure area in? We know that when we're measuring length we can talk about millimetres, centimetres, metres, and if we're talking about a very long length we might even talk about kilometres, if we were talking about maybe the distance between London and Birmingham.

We certainly wouldn't measure that in centimetres, it's too far, so we might use a much bigger measurement of length, like kilometres.

We use similar ones when we're measuring area, but remember I said that area is different, because it's not the distance from one point to another, it's the whole surface that something takes up.

So if you think about the room that you're in at the moment, if we were to measure the area of that room it would be all of the floor.

So maybe you've got carpet covering it.

All of that carpet would be the area of the room.

We couldn't measure that carpet just in centimetres, because that's the distance from one spot to another.

When we measure area, we measure surface, we measure it in things called millimetres squared.

So, or centimetres squared or metres squared or kilometres squared.

So we write it the same way.

We put a little two above it.

Now, the way I like to remember that is because the two tells us that we're talking about a 2D shape, and we're measuring that in units squared, so centimetres squared or metres squared, et cetera.

With these shapes here, you can see we've got five times two gives us 10 units squared.

And it's really important to remember to put that little two above the units to show that we understand that we're measuring area.

That other one on the side there, we've got three times five is 15 units.

And one times two is two units.

So you can see that our multiplication really helps us when it comes to measuring area.

Okay, so your task for today, if you have a look at this, this is what is on your worksheet, is to calculate the area of all the numbered sections on the floor plan and complete the table with the information.

So think carefully about these rectangles as arrays.

Think about how many rows and columns they've got and then work out, if you times one by the other, what the measurement will be, making sure that you write units squared to show that you understand you're measuring area.

Let me just take you back for a moment so that you can see what I mean.

So what you need to do is look at each of the rectangles on your worksheet.

You need to count how many squares it's being used across the length and then the breadth.

And then you need to multiply those together to give you the area.

Just like on these rectangles right at the beginning of the lesson, if I go to those blue dots, what I do to work out the area of that rectangle is count one, two, three, across, two down.

And three times two is six.

Gives me the area of that rectangle.

Just revising that here on this slide.

If I look at that big rectangle on the right there which says 15 units, that's because it's one, two, three across the top and five down the side.

Three times by five is 15.

So to work out the area of a rectangle, just like with arrays, think about them as rows and columns, we multiply one by the other and then we record it as units squared.

So pause the video here and see how you get on with your independent task.

Really well done for having a go at the independent task today, everybody.

Here are some of your answers.

Really fantastic work for having a go and working out the area of all of those shapes.

I'm not going to talk you through them as I'm sure you will get bored of the sound of my voice, but what I'll do is I'll leave it up for you to just have a look, pause the video if you'd like to, and see how you've got on with those answers.

So if you look at shape number one, you had to do, it was a long thin shape.

So it was 19 times by one, which is 19.

So hopefully you remembered to write units and put the squared at the top as well.

For some of the others, there was more multiplication needed.

So for question three, it was four times three.

So the length was four and the breadth was three.

It doesn't matter which order you do those in, you know that about multiplication.

You could do three times four as well, would have also give you 12.

And there were some others there, so question 12, five times five gives you 25.

Really well done for having a go at that.

It's quite a simple strategy for working out the area of rectangles.

Just like arrays, we're talking about multiplying the length and the breadth, and that will give us the whole area, the surface that that shape takes up.

I would love to see your working out for today.

I'm sure you're working out looks different to mine.

So if you'd like to, please ask a parent or carer to share your work on Instagram, Facebook, or Twitter, tagging @OakNational and #LearnwithOak.

I'd be really interested to see all your area working out from today's lesson.

Fantastic work today, everybody.

I'm really proud of how you've tried calculating area today.

Enjoy the rest of your learning, everybody.

Well done.

Bye bye.