Lesson video

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Hello there, I'm Miss Brinkworth.

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

Let's get started by having a look at the learning objectives together.

So what we're going to be doing, is we're going to be looking at the relationship today between area and perimeter.

We're going to use this knowledge to solve some problems. So, let's have a look at our agenda.

We're going to recap on how we calculate area and perimeter, we are going to solve area and perimeter problems, and there'll be time for an independent task as well.

So, let's have a think about what we need.

It's just a pen or pencil, pencil ideally, definitely some paper.

If you can find a ruler that'd be great, but if you haven't got one at home, please don't worry about it.

Pause the video here and get your equipment together.

Great, hopefully you've got everything you need.

Let's get started.

So just to get started on today's lesson, here you have some words, and on the other side, you have the definitions.

Try and match the word with the definition.

So think about what they all mean really carefully, and think about where that line is going to appear, to match the word with the definition.

Pause the video, take as long as you need.

Let's see how you got on.

Hopefully this was just a revision for you, but if you did find this a bit tricky, please listen carefully to what we mean, especially when we're talking about area and perimeter as that's what this lesson is all about.

So area is the space inside of a shape, it's surface.

So when we're talking about 2D shapes, the space that it takes up is the area.

If I was to give you a worksheet, covered in 2D shapes like squares, rectangles, circles, hexagons, and you colour them in, that space where you've done your colouring, would be the area.

What about the boundary then? Well that's the lines on a shape that mark the perimeter, and we have perimeter, which is the measurement all the way around the shape.

So we know we can add the sides together, and we will have worked out the perimeter.

A rectilinear shape, is one that's contains angles only right angles.

So those are the types of shapes that we've been looking at over these few lessons.

And then we know that a quadrilateral is a shape with four sides.

So well done if you've got all of those rights.

If you didn't, look at them a little bit more carefully, especially area and perimeter.

Okay, so making shapes with an area of 20 centimetres.

So we're looking at area now, and we're looking at different ways, in which we can make an area of 20 centimetres.

So we could have this type of shape, which is long and thin, because it's one by 20, one times 20 gives us 20.

So we know that that shape has got an area of 20, but there are other ways we can make this as well.

We could do two times 10 gives us 20, four times five gives us 20.

And we can see that the area, sorry, the shape has changed, the area has stayed the same.

What do you notice about all those numbers, that we use to make an area of 20? One and 20, two and 10, four and five? Well hopefully you can spot, that those are our factors of 20.

Our factor pairs, that when we multiply them together, we get the product of 20.

And that's because when we're working out area, we times together, the two sides, to give us the area to give us in this case, the product.

So bearing that in mind, can you have a go, at creating shapes with an area of 24? Thinking about, those factor pairs that would give you the product 24.

I wonder how many you came up with and if you were able to find them all.

So we know we can do one comes 24 and create a long thin shape.

There are other factor pairs of 24 as well.

We can half 24 to give us 12, so then we know our other side must be two.

So that two times 12 is 24.

Three eights are also 24, so well done if you found that one.

And then we have six fours as well.

So those are all our factor pairs for 24.

So that's pulling together, our knowledge on area and multiplication, and we've done an investigation there, where we can be sure those are all the ways that we can make rectangles with an area of 24.

Okay, what I'd like you to do now, is pause the video and have a think about these statements.

And think about whether they're true or false.

To do this, you will probably need to draw out some rectangles, and think about area and perimeter for each of them.

So that lady is saying, "the perimeter of a shape "will always be greater than the area." So have a go, draw some out and think about, will the perimeter always be greater than the area.

She's found one example there where that statement is true, but is it always true? Then think about the next statement that that person is saying in the blue top, "shapes which have the same area "would also have the same perimeter." So if you have two shapes with the same area, they must have the same perimeter.

These are two, quite complicated ideas, which will require you to do some working out.

So do pause the video and take as long as you need, to decide whether you think these statements are true or false.

Okay, let's have a look at these together then.

So that lady in the hat is saying, "the perimeter of a shape will always be greater "than the area." And she's given us an example there, where that's true.

She's got a shape there, which is four across and two down.

So the area is eight times two, sorry, the area is eight because it's four times two.

And the perimeter is 12 because it's two and four and two and four.

So she's found a rectangle there where her statement is true, but is it always true? She's used quite a small rectangle there.

If we move up into a larger shape, is it always true? So what I would do is draw another rectangle of a bigger shape, with larger sizes for the lines.

And I think is that true? For example, if I drew a rectangle, which was, or square, which was five by five, five times by five would give me my area, which is 25.

For the perimeter, I do five, four times, which is 20.

So as the rectangle gets bigger, it's not true, the perimeter is always bigger than area.

So her statement is not true because it's not always the case, that perimeter is greater than area.

Well done if you found that out.

Moving on to that other statement, "shapes which have "the same area, will also have the same perimeter." This is also, not always true.

We can move shapes round, and create different perimeters from the same area.

Okay, let's move on then to your independent task.

So what you need to do for your independent task is try some more investigations.

On your worksheet, there are some ideas, for you to try investigating, some rectangles, to draw and some working out to be done.

So pause the video here and have a go at your independent task and then come back together when you've completed it.

Well done for having a go at your independent task.

I'm hoping that on your paper, you've got lots of different rectangles drawn out, with different measurements on sides and different areas and perimeters, so that you've been able to investigate, all of those things on the independent task.

I can't go through the answers with you, because it will look completely different depending on what you come up with.

But what we would love to see is you're working out.

Cause this is the type of lesson where you're working out will be completely different to mine, completely different to somebody else's.

And we'd love to see how well you've got on, working out with different areas and perimeters.

So if you'd like to please ask your parents or carer to share your work on Instagram, Facebook, or Twitter, tagging @OakNational and #LearnwithOak, you've worked incredibly well today everybody, on your area and perimeter investigations, I've been really impressed, well done.

Thanks for learning with Oak today, and enjoy the rest of your learning, goodbye.