Lesson video

Hello, everybody.

My name is Mrs. Johnson.

I am so excited to be here today to help you with some of your maths learning.

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

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

This lesson is called "Describe, name and sort polygons, including pentagons, hexagons and octagons." It comes from the unit Shape: discuss and compare 2D and 3D shapes.

By the end of this lesson, you will be able to recognise, describe, and sort different polygons, including pentagons, hexagons, and octagons.

Don't worry if there are some words there that you haven't heard of before because I'm going to help you, and we will learn all about it together.

There are some important keywords that we are going to practise to get you ready for this lesson.

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

Ready? My turn, pentagon.

Your turn.

My turn, hexagon.

Your turn.

My turn, octagon.

Your turn.

Well done.

Listen out for those words today because they are going to be really important in this lesson.

There are going to be two parts to this lesson.

To begin with, you are going to learn about counting sides and vertices, and in a little while, you are going to learn to name and sort shapes.

Let's start with count sides and vertices.

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

Their names are Alex and Sam.

Listen carefully to what Alex and Sam have to tell you today because it will be really important for your learning.

Here are some shapes for you to look at.

These are all polygons because they are 2D shapes with straight sides.

I wonder if you can think of anything else about all of these shapes.

Do you notice anything that might be the same? Sam says, "Some of these polygons are tall and thin.

Others are wider.

I think these are different shapes." Alex says, "These polygons all have three sides and three vertices.

I think they are all triangles." Do you agree with Sam, or do you agree with Alex? Let's have a look.

These polygons are all triangles because they all have three sides and three vertices.

Alex was correct.

Counting the sides and the vertices of a polygon can be really helpful to help you find the name of that polygon.

If you look at these polygons and you count the sides, or you count the vertices, you see will see that they each have three sides and three vertices.

That means that these polygons are triangles because polygons with three sides are called triangles.

These polygons don't have three sides and three vertices, do they? That's right, all of these polygons have four sides and four vertices.

We know that these are called quadrilaterals because a polygon with four sides is called a quadrilateral.

Let's check that you can think about the number of sides that a polygon might have.

Listen carefully to this sentence.

I want you to decide, is this sentence always true, sometimes true, or never true? This is the sentence, polygons with four sides look the same.

Pause the video, and have a think about that.

Well done.

Let's see.

This sentence is sometimes true.

Let's have a look at an example.

These polygons both have four sides, and they look the same, so that would mean the sentence was true, wouldn't it? Polygons with four sides look the same.

If you have polygons like this, that is true.

But what if we have different polygons? Have a look at these.

These polygons all have four sides, but these all look different.

So the sentence was sometimes true, but not always.

Here is another polygon.

Sam thinks this polygon has six sides.

Alex thinks this polygon has five sides.

I wonder who is correct this time.

When you count the sides of a polygon, it can help to mark each side as you count, so draw a line on it as you're counting it to make sure that you don't miss any out.

It helps you remember where you started counting from.

Let's do that, and then we will know whether it's Sam or Alex who is correct.

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

This polygon has six sides, so Sam is correct.

Now, here is a different polygon for you to have a look at.

Sam thinks this polygon has seven vertices.

Alex thinks this polygon has six vertices.

I wonder who is going to be right this time.

Just the same as when you count the sides, you can mark the vertices as you count them too.

It will make sure that your counting is accurate.

Let's count the vertices together.

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

This shape has six vertices.

That means Alex is correct this time.

Let's check if you can count the sides of different polygons.

Which polygon has the fewest sides, and how do you know? Pause the video, and see if you can find which polygon has the fewest sides.

Let's have a look.

You needed to count the sides of each polygon before you can find out the answer to this question.

Let's count them together.

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

The first shape has six sides.

One, two, three, four, five.

This polygon has five sides.

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

This polygon has eight sides.

The polygon in the middle had five sides, so this polygon has the fewest number of sides because five is less than six and eight.

Well done if you chose the polygon in the middle too.

You've checked that you are good at counting sides.

Now let's check if you are good at counting vertices.

Do you think that this is true or false? This polygon has five vertices.

Pause the video, and have a think.

Let's count them together, and you can check if you've got this right.

One, two, three, four, five, six, seven, eight, nine, 10.

This is false.

This shape, this polygon, has 10 vertices.

Now it's time for you to practise counting the sides of some different polygons.

I would like you to tick all the polygons that have six sides.

You're going to need to count the sides really carefully.

Perhaps you could draw a little line on each side after you've counted it to make sure that you count them accurately.

If it has six sides, put a tick on that shape.

When you have finished that, you're going to have a think about these sentences here.

There are four shapes, A, B, C, and D.

They are all polygons, but they are different.

They have a different number of sides and a different number of vertices.

Can you write the letter of each shape in the space in the sentence? There is only one sentence for each shape, so when you have finished, you should have used all four shapes in your sentences.

The sentences are, mm is a quadrilateral.

Mm has more than six sides.

Mm has five vertices.

Mm has an even number of sides.

If you finish and you've written all four shapes into those sentences, I would like you to try and draw your own polygon and write a sentence to describe it.

You could use the sentences that are here to give you some ideas, but see if you can draw a polygon and write your own sentence to describe it.

You are going to try and do that now.

Off you go.

Well done.

Let's have a look and see if you have found all the polygons with six sides.

You should have this one.

This polygon has six sides.

Then you need this one next to it, and the first one on the second row too.

Then you need this one, this one, this one, and this one.

Those were all the polygons with six sides.

Did you remember to put a little mark on each side as you counted? That really helps to make sure that you are counting the sides accurately.

Well done if you remembered to do that.

Let's have a look at how you should have matched the shapes to the four sentences here.

The first one said, mm is a quadrilateral.

I know that a quadrilateral has four sides, so that must be shape C.

That's the only shape there with four sides.

Mm has more than six sides.

I'm looking for a shape with more than six sides.

I can see that the shape with more than six sides is A, so I'm going to put A on the second sentence.

Mm has five vertices.

I've got B and D left.

Which one has five vertices? I can see that is B that has five vertices, so I'm going to write B on my third sentence.

And finally, I do only have one shape left, so I think it should be D going in this space.

Mm has an even number of sides.

Let's just check.

D has six sides, and six is an even number, isn't it? So that must be right.

Did you notice that there was another shape that has an even number of sides? Sam noticed that C has an even number of sides too because it has four sides.

But C has already been used in the first sentence, hasn't it? And we did know that each shape has one sentence, so the shape with an even number of sides must be D.

You might have drawn your own polygon and written a sentence to describe it.

Maybe you drew something a bit like this.

You could have written, this polygon has an odd number of sides.

It has five sides, and five is an odd number.

You could have drawn something like this, and maybe you wrote, this polygon has eight vertices.

Well done for thinking so carefully about how you could count the sides and the vertices of those different polygons.

Now it's time to have a look at the second part of the lesson.

We are going to learn to name and sort shapes.

Sometimes you recognise a polygon and you know its name straight away.

Alex says, "I recognise all of these polygons." I wonder if you recognise them too.

The first one is a triangle, then the one in the middle is a rectangle, and the last one is a square.

Alex just knew all of those polygons because he recognises those shapes.

Do you recognise them too and you remember their names? That's really good.

Sometimes you don't recognise a polygon straight away and you cannot name it straight away.

That means you might look at a polygon and think, "Oh, I don't recognise that.

I'm not sure what the name of that shape is." If that happens, that is okay.

That's what's happened to Alex.

Alex says, "I do not recognise any of these polygons." But Sam says, "I have an idea to help us name these polygons." So if you don't recognise a polygon straight away, it is not a problem.

We're going to listen to Sam and see what her idea is.

Sam says, "Let's count the sides." One, two, three, four, five.

Five sides.

One, two, three, four, five.

Five sides.

One, two, three, four, five.

Five sides.

They each have five sides.

Even though we didn't recognise these shapes and they all look different to each other, we can say that all of these polygons have five sides.

Sam knows a polygon with five sides is called a pentagon.

That means that all of these shapes are pentagons.

Pentagons don't always look the same as each other, but they always have some properties that are the same.

A pentagon will always have five sides, and a pentagon will always have five vertices.

Look at all of these pentagons.

They all look very different, but they all have five sides, and they all have five vertices.

That's what makes them all pentagons.

Let's check if you can spot the pentagon.

Do you think it's A, B, or C? And how do you know that that shape is a pentagon? Pause the video, and have a think.

Let's have a look.

The shape that is a pentagon is B.

Sam says, "I counted the sides.

B is the pentagon because it is the only polygon with five sides." Is that what you did too? If you look carefully at A and you count the sides, you can see that it has six sides, and C only has four sides.

A pentagon needs to have five sides, so B is the pentagon.

You can count the sides or the vertices of a polygon to help you name it.

Let's have a look at these polygons and see if we can find out what these are called.

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

Six sides.

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

Six sides.

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

Six sides.

These polygons each have six sides.

Sam knows that a polygon with six sides is called a hexagon.

All of these polygons are hexagons.

Hexagons do not always look the same as each other, but they always have properties that are the same.

What do you think those properties are going to be that are always the same? Let's have a look.

A hexagon always has six sides.

A hexagon always has six vertices.

They can look really different to each other, but they will always have these properties the same.

They always have six sides, and they always have six vertices.

Let's check if you can spot which polygon is a hexagon, and how do you know? Is it A or B or C? Pause the video, and have a think.

The polygon that is a hexagon is C.

You needed to count the sides or count the vertices and find the polygon that had six.

A only has five, and B only has five, so the hexagon is C because it has six sides and six vertices.

Let's check if you can remember.

What does a hexagon need to have, and what does a pentagon need to have? These polygons have been sorted into sets, but one of them is in the wrong place.

Pause the video, and see if you can find which one is in the wrong place.

Let's have a look.

Do you think you have spotted it? Did you count the sides or the vertices of each polygon? That would help you to find which polygon is in the wrong set.

This polygon here only has five sides and five vertices, but it has been put in the hexagon set, and that's not right.

If it has five sides and five vertices, it is a pentagon.

You know that you can count the sides or the vertices of a polygon to help you name it.

I wonder what's going to happen when we count the sides or the vertices of these polygons.

Let's have a look.

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

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

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

Each of these polygons has eight sides.

Sam knows that when a polygon has eight sides, it is called an octagon.

Octagons do not always look the same as each other, but they always have some properties that are the same.

I wonder if you can think about what they might be.

An octagon will always have eight sides, and an octagon will always have eight vertices.

Well done if you were thinking about that too.

Let's check if you are good at spotting octagons.

True or false? These polygons are all octagons.

There's one, there's another one, and there's the last one.

Are these polygons all octagons or not? Have a think about how you might check.

Pause the video, and see if you can decide if this is true or false.

These polygons are all octagons.

I wonder what you did to check whether these polygons were octagons or not.

Did you do some counting? Let's see what Sam did.

Sam said, "I counted the sides." Maybe you counted the sides too, or maybe you counted the vertices.

Sam found that they each have eight sides, so this is true.

They are all octagons.

They look different, but they are all octagons because they each have eight sides and eight vertices.

You have now learned about three different names of shapes in this lesson.

The words pentagon, hexagon, and octagon sound quite similar, don't they? Sometimes people can find it a little bit confusing or a little bit tricky to remember all of these words, so it can be helpful to have your own way of remembering the properties of each polygon so that you can name them correctly.

Sam has a special way that she likes to remember one of these names.

Let's have a look at that now.

Sam says, "I know that an octopus has eight arms." Here is an octopus.

You can see the eight arms on the octopus.

Alex has noticed that octopus and octagon both start with "oct." Octopus, octagon, they both have "oct" at the start.

"Oct" links with eight.

If Sam knows that an octopus has eight arms, that will help her remember that an octagon has eight sides and eight vertices.

Alex has got his own special way of remembering the properties of a hexagon.

Alex noticed that hexagon and six both have the letter X.

There is six and hexagon, and they both have an X.

If you think about the sentence, a hexagon has six sides and six vertices.

You can see that letter X.

The names for the other shapes don't have the letter X in, do they? So Alex can remember that when he sees the X in hexagon, it will remind him of the X in six, and that helps him to remember that a hexagon has six sides and six vertices.

Sam has a special way of remembering the properties of a pentagon.

Sam noticed that all of these shapes have "gon" at the end of their name, hexagon, octagon, pentagon.

They all have "gon" at the end, don't they? Sam also noticed that the word pentagon has five letters before "gon." One, two, three, four, five.

This helps Sam to remember that a pentagon has five sides and five vertices.

The other names of the shapes don't have five letters before "gon." Only pentagon does, so that helps Sam to remember that a pentagon has five sides and five vertices.

Do you have any special ways of remembering these shapes? I wonder if you can think of your own special way of remembering these names, or maybe you like some of the special ways that Alex and Sam have shown you to help you remember these shape names.

Let's check that you can match the polygons to the correct names.

You have hexagon, octagon, and pentagon.

Which polygon should you match up with each name? Pause the video, and see if you can match those up correctly.

Good thinking.

Let's have a look.

The hexagon is this shape here because it has six sides and six vertices.

The octagon is the shape in the middle.

It has eight sides and eight vertices.

The pentagon is the shape at the top.

It has five sides and five vertices.

Now it's time for you to do a little bit more practise.

You are going to look carefully at these polygons and then at the sentences underneath.

In each box, you need to decide whether you should write octagon, pentagon, or hexagon to match the polygon or to complete the sentence.

When you have finished that, you're going to have a go at using a ruler to complete each polygon so that it has the correct number of sides and vertices.

In the first box, you need to draw two different hexagons.

In the middle, you are going to draw two different pentagons.

And in the last box, you need to draw two different octagons.

Try and remember how many sides and how many vertices a hexagon, a pentagon, and an octagon should have.

You can see that the first three sides of each polygon have already been drawn for you.

You need to draw the rest of the polygon.

See if you can find at least two different ways to complete each polygon.

Make sure you have a ruler and a pencil ready.

Off you go.

Well done.

Let's have a look and see if you have written octagon, pentagon, and hexagon in the right places.

The first shape was a hexagon, the next one is a pentagon, and the next one is an octagon.

Next to that, you have another octagon, and then a pentagon, and then a hexagon.

In the sentences, you need to say an octagon always has eight sides and eight vertices, a hexagon always has six sides and six vertices, a pentagon always has five sides and five vertices.

Well done if you have written the correct shape name in each box.

Good work.

On the second task, you might have completed your polygons like this.

Did you notice that three sides of the polygon are already drawn? Maybe you thought, "I know that a hexagon has six sides.

I need to draw three more sides because 3 plus 3 is equal to 6." You need to draw three more sides.

Maybe you drew it like this, or perhaps you drew it like this.

Maybe you found another different way.

Just check that your hexagon definitely has six sides and six vertices.

When you got to the pentagon box, you should have been thinking that "I can see three sides already drawn, and a pentagon has five sides.

That means I need to draw two more sides because 3 plus 2 is equal to 5." You only need to draw two more sides this time.

Maybe you drew something like this, or like this, or you might have found another different way to do it.

With the octagons, again, you would have been thinking, "I can see three sides already drawn.

An octagon has eight sides.

That means I need to draw five more sides because 3 plus 5 is equal to 8." If you need to draw five more sides, you might have tried to do something like this, or maybe you could have tried something like this, or again, you might have found another different way to draw your octagons.

Make sure that your hexagons have six sides, your pentagons have five sides, and your octagons have eight sides.

Well done for thinking so carefully about how you might be able to draw those different shapes.

Now that you're at the end of the lesson, you have learned that you can count the sides and the vertices of polygons to help you find the name of the shape.

It is a good idea to mark them as you count so that you don't make a mistake and you can make sure that you count them accurately.

A polygon of the same type can look very different, and you might not know the name of the polygon just by looking at it.

You might not recognise the shape.

You need to look at the properties of the shape.

That means you need to count how many sides and how many vertices.

You know that a pentagon has five sides and five vertices, a hexagon has six sides and six vertices, an octagon has eight sides and eight vertices.

I love that you have tried so hard today, and you have really tried to start using some of these important shape names when you are talking about polygons.

Well done.

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

Bye, everybody.