Lesson video

Hi, I'm Miss Kid Rossiter.

And I'm going to be taking your lesson today on describing areas.

It's building on the work that we've already done on describing perimeters.

And it's the second in our series of area and perimeter of 2D shapes.

Before we get started, please make sure you're free from all distractions, you're in a nice, quiet place if you're able to be, and you've got something to write with and something to write on.

If you need to pause the video now to get it sorted, then please do.

If not, let's get going.

So starting today's lesson with a Try this activity.

What is the same about all of the shapes on your screen? What is different about all of the shapes on your screen? And then once you've answered those questions, can you draw some more shapes that are also made out of these square units? That have similarities and differences to the shapes on the screen? Pause the video now and have a go at this task.

Excellent, what did you work out? What was the same about all three of these shapes? Tell me now? Excellent, there are a few things that you could have noticed there, but I noticed that they were all made of nine squares, so they were all made of nine squares.

So that means that they have an area of nine squares.

If you're not quite sure what area means, don't worry at the moment cause we're going to come onto that slightly later in the lesson.

What's different about all the shapes then? Maybe you could have drawn on your knowledge from last lesson that we did about perimeter.

So these shapes all have different perimeters, don't they? Well, actually not all of them do.

One of them is different.

So this shape in the middle has a perimeter of 20 units.

And then the shape on the left and the shape on the right both have parameters of 14 units.

Did you manage to draw some other shapes that had similarities and differences to these? Excellent work if you did, well done.

So moving on to area then, so the area of a shape is a measure so the area of a shape is a measure of the space inside its boundary.

So this is a really important definition.

So I would like you to pause the video here and write this down.

Excellent work, well done.

So we're going to move on then, which of these shapes that are on your screen, have the same area? Pause the video here and try and work out the area of each shape and then explain how you know, what shapes are the same and what shapes are different? So pause now and have a go at that task.

Excellent work, well done.

So these are your areas that you should have worked out.

How did you think about working out the areas? What did you do? So one way that you might've thought about it for these shapes, is that you would count the squares inside the shape and also count the half squares.

So I'm just going to make a note of that, you might want to make a note of that as well.

So count the squares and half squares.

So count the squares and half squares.

Cause that was easy for me.

All the space inside these shapes was All the space inside these shapes was either a full square or half a square.

So for example, here, I had one full square, two full squares, three full squares, and then half a square here.

This one, again, I had one full square, another full square, and then a half, and then another half, which adds to three all together.

These two though, these two triangles were slightly trickier in my opinion.

How did you work out the area of those? Can you tell me now? Excellent, you might have thought about it the way I thought about it, which was to make it into a rectangle.

And once I've made it into a rectangle, I could count the squares.

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

I could count the squares.

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

And I knew that the triangle would be half of the rectangle.

So I counted squares So I counted squares for the rectangle, and then halved.

Excellent work on that, you're now going to apply what you've learned to the independent task.

So pause the video here, navigate to the independent task, and when you're ready to go through some answers, resume the video.

Good luck.

How did you do with that independent task? Did you give it a good go? Let's go through question one then.

So the first one has got five square units.

That's the area.

The second one is 4 1/2 square units.

And the third one, let's just do that one together.

We've got one square unit here, a second square unit here, a third square unit here and a fourth square unit here.

And then we've got half a square unit here and half a square unit here so altogether we have five square units.

Draw a rectangle with the same area as this quadrilateral.

So first of all, we needed to work out the area of this quadrilateral.

So let's just do that together.

So we've got one square unit here, we've got half a square unit here and here so that's two so far.

And then we've got these parts units.

Hopefully you realised that this one here and this one here made up a square unit.

This one here, and this one here made up a square unit.

These two made up a square unit and these two made up a square unit.

So in total, you had six square units here.

So you had to draw a rectangle with the same area so you could have drawn this one, which is a 3 x 2 rectangle, which is a 3 x 2 rectangle, or you could have drawn this one, which is a 6 x 1 one rectangle.

They're the only two options there if you're using integer number of squares on the sides, but you could have, for example, done a 1 1/2 squares by what? Excellent four, so you could have done four across and then 1 1/2 down.

and then 1 1/2 down.

That would also be six square units, wouldn't it? Good work.

Find the area in small triangles of these two shapes and then which one is bigger.

So the blue shape, which is this one here on the left hand side, had an area of 22 triangle units.

And the green shape here had an area of 24 triangle units so that means that the green shape has the larger area.

Excellent work, so moving on to the Explore task now then.

For each one of these diagrams, you need to decide whether the purple or the pink shaded area is greater? And then can you explain to me how you know? If you feel confident with this activity, pause the video now and get on with it.

If not, just stay tuned and I'll give you a little bit of support on the next slide.

If you need a little bit of support, that's absolutely fine.

That's what I'm here for.

So we're looking for units that are the same within both shapes.

So on this paper that I've got here, I've got these triangular units where if I join from dot to dot, you can see that they create these triangular units.

you can see that they create these triangular units.

So can you count how many triangular units I've got inside this purple shape? And then once you've done that, can you do the same for the pink shape? Then for the other two diagrams, what shape units could you use to compare them this time? So pause the video here and have a go at this task.

Excellent work everyone, let's go through it together then.

So you should have for the first one realised that the area of the purple triangle there is 16 small triangles where our small triangles are this shape here, are this shape here, and we've got 16 of those inside.

And then for the pink shape, we've also got 16 small triangles so for these ones, they are the same.

They have the same area.

This one here then, we've got our square units this time.

This one here then, we've got our square units this time.

So our purple shape has an area of eight small squares and our pink shape has an area of nine small squares, and our pink shape has an area of nine small squares, so the pink shape has the greater area here.

And then finally this time we're looking at hexagonal units.

So the purple shape, which is this one here has an area of 2 1/2 small hexagons and the pink shape, which is this one here, has an area of two small hexagons, so that means that the purple shape has a greater area.

That's the end of today's lesson.

So thank you very much for all your hard work.

I hope you've enjoyed it as much as I've enjoyed teaching it to you.

Please don't forget to go and take the end of lesson quiz so that I can see what you've learned and hopefully I'll see you again soon.

Bye.