Lesson video

Hello everybody.

My name is Mrs. Johnson.

I am really happy to be here today to help you with some of your maths learning.

I hope you are ready to work hard and have lots of fun.

Let's see what we are going to be learning about today.

This lesson is called investigate how polygons can be joined and folded to form 3D shapes.

It comes from the unit Shape: Discuss and compare 2D and 3D shapes.

By the end of this lesson, you will be able to investigate how polygons can be joined and folded to form 3D shapes.

This is a really exciting lesson because you are going to see how you can actually create your own 3D shapes from 2D shapes.

There are some important keywords that we need to practise so that you are ready for your learning today.

I will say them first and then it will be your turn.

Ready? My turn, 3D.

Your turn.

My turn, three dimensional.

Your turn.

My turn, 2D.

Your turn.

My turn, two dimensional.

Your turn.

My turn, face.

Your turn.

Well done.

Did you notice that for two of our key words, there are two different ways to say them.

There is a shorter way and there is a longer way.

You can say 3D, which means three dimensional and you can say 2D, which means two dimensional.

There are going to be two parts to this lesson today.

To begin with, you are going to learn about 2D shapes in 3D shapes and then in a little while you are going to learn about building 3D shapes from 2D shapes.

Let's start by looking at 2D shapes in 3D shapes.

There are two friends who are going to help in this lesson today.

Their names are Sofia and Jun.

Listen and watch carefully because Sofia and Jun have lots of important things to show you today.

Sofia and Jun have collected some 3D shapes.

We can see them here, can't we, the shapes that they have collected.

3D shapes are sometimes called solid shapes because they are not flat.

If you hold 3D shape between your hands, you can feel it taking up space.

That's how you know that it's a 3D shape.

Jun says, "I have an idea for a game that we could play with these shapes." I wonder what game they're going to play.

Let's have a look.

Jun says, "I will choose a 3D shape and dip it in paint.

Then I will press it onto the paper.

You have to guess which shape I chose." Ooh, let's see what happens.

This is the painting that Jun has made.

Look at this.

He's created a 2D shape with his paint.

Sofia says, "I can see a 2D shape.

It is a rectangle.

I think you chose this 3D shape." Sofia can see that the painting that Jun has created is a rectangle and that this 3D shape has a rectangle on it.

They're going to play again.

Jun is going to choose a different shape and dip it in the paint.

Press it onto his paper.

This is the painting that he has created.

Look at this 2D shape.

Sofia says, "I can see a square, so I think this is the shape you chose." Do you think she's right? Jun says, "No, that is not the shape I chose." It could have been a match.

This 3D shape does have squares on it, but this is the one that Jun chose.

He says, "Are there any other shapes that have a square face?" Let's have a look at them again.

Can you see any other 3D shapes that might have a square face? Sofia's going to choose again.

She says, "Could it be this one? I can see a square on the bottom." Jun says, "Yes, you are right.

I chose the pyramid." Jun is going to choose another shape and dip it in the paint.

Press it onto his paper and this is the 2D shape that he has created this time.

Sofia knows this is a rectangle, so she thinks this is the shape that Jun chose.

Do you think that she's going to be right this time? Oh, unlucky, Sofia.

Jun says, "No, that is not the shape I chose." The shape Sofia chose could have been correct.

It did have a rectangular face, but Jun says that wasn't the one he chose, so Sofia needs to have a look again.

Are there any other 3D shapes with a rectangular face like this? Sofia's going to have a look and she says "It must be this one.

This shape also has a rectangle." Jun says, "Yes, you are right.

I chose the cuboid." Let's check if you can work out which shape could Jun have chosen when he created this painting of this 2D shape.

There might be more than one that Jun could have chosen, so pause the video and have a think.

Let's go along each 3D shape and have a look.

It can't be the first one.

It can't be the second one.

Neither of those have a triangular face and Jun's 2D shape that he has created is a triangle, isn't it? So it can't be either of the first two shapes, but it could be this one and it could be this one.

Both of these 3D shapes have a triangular face, so Jun could have chosen either of those to create his triangle painting.

Now it's time for you to practise and you are going to have the chance to explore making prints with 3D shapes.

You will need to have a selection of different 3D shapes or objects.

You could dip them into paint or you could press them into playdough or you could place them on a piece of paper and draw around them.

When you've done that, have a look and see if you can name the 2D shape that you have created.

For example, if you chose this shape, you could dip it in paint.

You could create a 2D shape and you could say, I have created a square.

I wonder how many different 3D shapes will you be able to use and how many different 2D shapes will you be able to create? Pause the video and have a go at that now.

Let's have a look at what you could have done for this practise.

Sofia chose to stamp her 3D shapes into some playdough.

These are the shapes that she had and if you look in the playdough, you can see the different stamps that she made.

Sofia said, "I created lots of different rectangles with my 3D shapes.

I also created a triangle and a hexagon." Sofia was able to name all of the 2D shapes that she created with her 3D shapes.

Did you think about what you could name your 2D shapes too? Well done if you did.

Now it's time for the second part of this lesson.

Now you are going to learn about building 3D shapes from 2D shapes.

When Jun dipped his 3D shape into paint and printed with them, he created 2D shapes.

When Sofia pressed her 3D shapes into her playdough, she created 2D shapes.

Jun says, "I think this means that 3D shapes are made by joining 2D shapes together." Do you think Jun is right? Could you make a 3D shape by joining 2D shapes? Let's have a look.

Jun wants to make a model of this 3D shape.

He needs to think about the shape of each face.

He says, I could use paint to make a print of each face to help me see the 2D shapes that I will need.

He can see that this shape has two triangular faces and three rectangular faces.

Now, Jun could use some construction materials to make this 3D shape.

Which 2D shapes would he need to use? Hmm, I wonder.

I think Jun might have just done something that would help him to choose which shapes he needs, hasn't he? Sofia has remembered.

She says, remember to use your painting to help.

Jun made a painting, didn't he, where he could see the shape of all the faces.

Jun will need two triangles and three rectangles if he wants to build this 3D shape.

He's going to take his two triangles and three rectangles to build this 3D shape.

Jun is looking carefully at the 3D shape and he can see that the triangular faces are at the ends, so he's going to place his triangles at the two ends of one of the rectangles.

He can see that the rectangular faces are around the middle, so he's going to join those together down the middle.

Now, Jun says "I can fold and join them to build a 3D shape." Let's watch Jun fold them up and join them together and see if he can make this 3D shape, ready? He can.

He has joined his construction materials together and he has made a model of this 3D shape.

Let's check that You can spot the correct painting which shows all the faces of this 3D shape.

Do you think it could be a, or b, or c? Pause the video and have a go.

Well done if you said b.

We can count the faces on this 3D shape to show that b is definitely the right painting to show all the faces of this shape.

We can see one, two, three, four triangular faces.

There are only four because now we can see we've got back to the first one.

There are four triangular faces.

There is one more face and it's underneath, isn't it? If we lift up that shape, we can see there is one square face underneath.

That is how we know that b is definitely the right painting to show all the faces of this 3D shape.

Now, let's check.

If you can imagine when Jun folds up these construction materials and joins them together, which 3D shape do you think he's going to make? Could it be a, or b, or c? Pause the video and have a think about that.

The 3D shape that Jun is going to build is c.

You know that the shape Jun is going to build is c because if you look at his construction materials, you can see that there are going to be four rectangular faces and two square faces.

If you look at shape a, it hasn't got any square faces.

If you look at shape b, it has six square faces.

Neither of those would match the shapes that Jun has in his construction materials, so the 3D shape that Jun would build is c.

Well done if you said c.

Jun has found some more 3D shapes.

He wants to try and build these from his construction materials.

Do you recognise any of these 3D shapes? There is a sphere, a cone, and a cylinder isn't there? Do you think Jun is going to be able to make these 3D shapes with his construction materials? Sofia says, "I don't think you're going to be able to do that." She doesn't think that Jun can make these 3D shapes with his construction materials.

Do you agree with Sofia? Let's have a look.

These 3D shapes have a curved surface and Jun's construction materials are polygons.

That means that they are flat 2D shapes with straight sides.

When polygons are joined together, they make 3D shapes where all the faces are flat.

You can't use flat polygons to build a 3D shape that has a curved surface.

You can only build 3D shapes with flat faces in this way.

Let's check if you can spot which 3D shapes could Jun build with his construction materials? Could he build this one, this one, this one, and this one? Pause the video and have a think.

Jun could not build the first shape because it has a curved surface.

He could build the second one using his squares.

He could not build this one because this has a curved surface.

He could build the last one.

He would need a square and four triangles, wouldn't he? Now it's time for you to practise thinking about building 3D shapes from 2D shapes.

First, you are going to match the 2D shapes to the 3D shapes that they will make when they are folded and joined together.

When you've done that, you are going to use your own construction materials or you can cut and fold some pieces of card if you don't have any construction materials to explore, building your own 3D shapes.

See if you can think about how many shapes can you build that have more than one square face, and how many shapes can you build that have more than one triangular face.

Pause the video and go and try that now.

Well done for looking so carefully at these 2D shapes and 3D shapes and thinking about which 2D shapes would create each of these 3D shapes.

Let's have a look and see if you've matched them up correctly.

The first one would build a pyramid because it has one square face and four triangular faces.

The next one would build this 3D shape because it has three rectangular faces and two triangular faces.

The last one would make a cube.

We can see that on these 2D shapes, they have only used squares and we know that a cube is made up of square faces.

On the second question, you might have had a go at using construction materials to build some different shapes, especially trying to find how many shapes you could make that had more than one square face.

Did you try joining six squares together like this and folding them up to build a cube or maybe you tried to join some rectangles and some squares together so that you could make a cuboid? Did you try and make a shape that had more than one triangular face too? You could have started with three rectangles and two triangles and folded it up to make a 3D shape like this, or maybe you tried a square with four triangles and you made a pyramid.

Well done for trying out different ideas and really thinking about building 3D shapes from 2D shapes.

Now that you are at the end of the lesson, you know that 3D shapes can have flat faces and each face is a 2D shape.

You can have shapes with rectangular faces, triangular faces, square faces.

You have found out that you can fold and join 2D shapes together to build different 3D shapes.

Well done for your hard work today.

I hope that I will see you again soon for some more math learning.

Bye.