2D and 3D shapes: To Build Simple 3-D Shapes

Key Stage 2

Maths

2-D and 3-D shape

How many vertices can be found on a rectangular prism?

What shape is represented by this part image?

How many edges does an octagonal prism have?

How many faces does a square based pyramid have?

﻿Hi everyone. I'm Miss Miles and welcome to your math lesson. Before we start, a did you know fact. Today's fact is, did you know a Welsh mathematician created the is equal to sign in 1557? Okay back to the maths. Please make sure that before you do today's lesson you have completed the pre lesson quiz. For our lesson you will need a pencil, a piece of paper, and you will need a clear work space. In today's lesson we will be learning to build simple 3D shapes. Let's get started. On the screen now, you will see a net of a shape. A net of a shape is something that we can fold together to create a 3D shape. If we look at the net on screen it is made up of some different faces and then these parts around the edge, are the tabs. And if we were to fold them, they would help us to put our 3D shape together. So when we're trying to identify which 3D shape is represented by a net we need to look at the full faces that we can see here. So my question to you is, what 3D shape will this net become? In order to do that, we need to count the faces that we've got. We need to identify the shapes that make up the net. And then you need to use your knowledge of 3D shape properties to identify what shape it will be. So I would like you to look at the net on screen. Look at the different faces and what shapes they are. And see what 3D shape you think it could be. Pause your video there. Okay, I know that this 3D shape is going to be a cube. Now I know that because I know a cube has one, two, three, four, five, six faces that are all square and are all of equal size. And I can prove that because I've got a cube here with me. So here's my cube. It has one, two, three, four, five, six square faces. And my net on screen also has six square faces. This square here would form the base. This square here would form this face here because it would fold up. These two square faces here would fold around to form these two side square faces. And these two here would fold up and up to the top to finish our cube. So that net forms a cube. Let's have a look at another one now. Here is a different net of a different 3D shape. Bearing in mind what we talked about before, I would like you to identify what 3D shape this net will make. Pause your video there. Okay so looking at the net on screen, I can see one, two, three, four, four triangular faces. Now I can only think of one 3D shape that has four triangular faces. Looking at my net, I also know that this triangle here would form the base of my 3D shape. Now what shape do I know that has a triangular base? I think it could be a triangular-based pyramid. I've got one here with me. Shall we see? So here is my triangular-based pyramid. It has a triangular face at the bottom. And then one, two, three triangular faces around the edge. So here's my triangular base. Matching my triangular base here. And then one, two, three triangular faces that would fold up around the edge. So this net would create a triangular-based pyramid. Did you get the same answer as me? Okay, onto another this time. So here is another net on the screen. Again have a look at the different faces and see if you can work out what 3D shape this would make. Pause your video there. Okay hopefully you might notice that this net also creates a cube. We looked at a net for a cube earlier, but this is another net, a different net that would also create a cube. And again, let's prove it together. So here's my cube from before. Let's have a look at our faces again. One, two, three, four, five, six square faces that are all identical. Let's double check that that's the same as this. One, two, three, four, five, six square faces that are all identical. So I know that the properties of the net match the properties of my 3D shape. And if I were to fold it together, I know that I would end up with a cube. Okay. Now let's think about this slightly differently. Which of these three nets on the screen would make a square-based pyramid? So it's a little bit tricky because I know that a square-based pyramid has a square face and four triangular faces. And all of those nets on screen have one square face and four triangular faces. But which ones actually would make a square-based pyramid? And can you explain? Pause you video there and have a think about it for me. Okay. Let's have a look through all of these nets then. So the first net I think would make a square-based pyramid because here is my square base. I've got a square-based pyramid here to show you. Here's my square base. And then is has its four, one, two, three, four it has it's four triangular faces around the edge that would fold in. So we've got one, two, three, four triangular faces around the edge. And if we folded them in, they would create my square-based pyramid. Okay the second one. Now the second net on screen is very similar to the first however the fourth triangular face here is attached to this triangular face. Leaving this side of the square face blank. Meaning there wouldn't be a face attached to that side. So that one can't be a net for a square-based pyramid. Okay let's have a look at the fourth one, oh the third one sorry. So here again is my base in the middle. Here's my base and then around the edge I've got four triangular faces. So these two here would fold in to create two of my triangular faces leaving spaces here and here. And then this triangle would fold around to meet this one. This triangle would fold around to meet this one. So that one would also create a square-based pyramid. So number one and number three, but number two would not. Did you get the same as me? Okay, let's have a look at another shape now. So which of these nets would make a pentagonal prism? Okay, there's a pentagonal prism on screen. And I've also got a pentagonal prism here to show you. So let's just have a quick look at it. So we've got a pentagon here and I've got another pentagon here and then I've got rectangles around there. So have a look at the three different nets on screen. Pause the video and see if you can work out which nets would create that pentagonal prism. Pause you video. Okay, so net number one. I know that net number on would make a pentagonal prism. And I know that because there is a pentagonal face at each end. So here's one of my pentagonal faces and here is the other. And they are connected by a rectangular face in the middle. Just like mine is. And the the other one, two, three, four rectangular faces would then join to connect the two pentagonal faces. So number one is correct. Net number two is also correct because there is a pentagonal face at each end. And we would fold around all the rectangular faces to joint them together to create a pentagonal prism. So number one is correct. Number two is correct. However number three is not correct. And I know that simply because there is not a pentagonal face at each end of the rectangles. Okay because they're connected. So because they're connected, that cannot make a pentagonal prism because my pentagonal face here is not connected to another pentagon. So that cannot be right. Did you get the same answers as me? Okay time to apply our learning to an independent task now. Here are the nets of nine solid shapes. Each of these has been cut into two pieces. So a whole net has been taken and split into two parts. Can you see which pieces go together? So you need to have a look at the nets on screen. Find two that would match together to would make one net for one 3D shape. Pause your video there and have a go at that for me. Okay, how did you get on with that? Let's go through the answers. So there are quite a few different 3D shapes made by these nets. Let's have a look through the answers together. So the first shape is a cube made by nets E and K. The second shape is a cuboid made by nets C and P. Then we have a tetrahedron or triangular-based pyramid made by L and M. Then a square-based pyramid made by nets B and F. A pentagonal pyramid made by nets D and N. A hexagonal-based pyramid made by nets O and S. We have a triangular prism made by nets G and Q. A pentagonal prism made by nets J and R. And a trapezoid prism made by nets A and H. So have a look at the answers that you've got and compare them with the answers on screen. And make any corrections if you need to. Well done for completing today's lesson. Don't forget to complete the end of lesson quiz. And I'll see you again really soon.

2D and 3D shapes: To Build Simple 3-D Shapes

2D and 3D shapes: To Build Simple 3-D Shapes

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UnitMaths / 2-D and 3-D shape

Maths