Lesson video

Hi, it's Mr. Etherton here, and welcome back to another exciting week of our maths learning.

Today, our learning outcome is to be able to describe 2D shapes based on their properties.

So let's look at this a bit further to find out what we'll be doing in today's lesson.

In today's lesson, we will recap what the various properties of the 2D shapes are, and begin to identify them within 2D shapes.

So we're going to be using all of our knowledge from last week to describe 2D shapes.

We're also going to think about how we can work effectively, efficiently, and systematically.

As always, we need to be prepared for our learning.

So today you will need a pencil, a piece of paper, or an exercise book to do your working out, and if you still have one from last week, you will need an angle detector.

Don't worry if you don't have an angle detector, I'm going to show you what you need to make one of these.

So to make your angle detector, you need two strips of card like this.

This doesn't have to be card, it could be another material in the same shape.

And then we are going to put them together on top of each other, and use our split pin here to push a hole through the end so that it lines up.

And then our angle detector should be able to move all the way around like this.

I've seen some different versions of these, maybe using a hoop or a key ring to attach your materials.

Also, you could just use a corner of a piece of paper to be more specific with those right angles.

So please pause the video now, to get all your equipment ready.

Brilliant, year three, let's have a look at our learning.

So if you haven't done so already, what I would like you to do at the beginning of this lesson is complete our introductory knowledge quiz.

So please pause the video to complete that quiz now, if you've already completed the quiz, continue watching.

So to start our learning today, we are going to do a super quick warm-up.

So you will need your pen or pencil, and your paper to complete this.

During this warm-up, what I would like you to do is look at the shapes on your screen, A B, C, D, and E.

I would like you to name those 2D shapes.

To help you, you might want to count the number of sides on those shapes.

I'm going to give you one minute.

So complete this activity, pause the video, go.

Brilliant, welcome back year three.

Let's have a quick look through some of our answers.

So the answer to A, I would like you to shout that at the screen now.

Fantastic, if you said it was a pentagon.

Remember pentagon means having five sides, well done.

So B, shout out the answer.

Well done, I heard a lot of you shouting hexagon.

Fantastic! And we can remember that one because in the word hexagon, we have an X and in the word six, we also have an X in the spelling.

And what do we think C is? Well done to those of you that said it is a square.

It's not a diamond or a kite.

This is a square that has been tilted onto its side.

We can double check that because I can see that it's got four sides that are of an equal length, and all the angles are right angles.

That means it is a square.

D and E were quite tricky.

So D if you've got this correct, well done, it was a trapezium.

We're going to be exploring this shape a little bit later.

And E, well done if you've got this one as well, it is a parallelogram.

You might recognise a word within that.

The word parallel, meaning lines that stay the same distance apart.

If we have a look at this 2D shape, we can see that it has two pairs of parallel lines, and each set of parallel lines has a different length.

Also the opposite angles in our parallelogram are equal as well.

So again, we're going to be investigating that shape a little bit further in today's lesson.

So as always, we're going to go through our star words.

So we're going to do my turn, your turn.

I want to hear nice and loud repeating after me.

So right angle, acute, obtuse, parallel lines, and perpendicular lines.

Brilliant, thank you to everyone that joined in really loudly with those star words.

So let's recap what some of those words mean.

A right angle, remember a 90 degree angle that can be found within our shapes.

It kind of looks, when the two lines make an L shape, a perfect L, and we can fit that squared off angle in the corner is our right angle.

An acute angle, this picture might help you remember, is an angle smaller than a right angle.

One way I always remember this, is I think about babies.

And when I look at a baby, I think, oh, a baby's quite cute.

And a baby is quite small.

That helps me remember that acute angles are smaller than right angles.

Obtuse is an angle greater than a right angle, so our more open angles.

Parallel lines, we've mentioned that briefly, when two lines run alongside each other, but they never meet, they will never touch.

Even if we continue those lines, so that opposite each other.

And then perpendicular lines, this is when one line and another line join together at a perfect right angle.

This creates a pair of perpendicular lines.

So whenever we see right angles, we also we'll see perpendicular lines.

And all of these words are properties of 2D shapes.

You might've remembered that word from last week.

So we use these words to describe our 2D shapes.

That's what we'll be doing today.

So, let's learn.

On the screen in front of you, I would like you to try and identify what shape I have represented.

I'll let you quickly count the number of sides, and see if you can remember its name.

I'll do a quick countdown.

Well done, if you've remembered that this is a pentagon, because it has five sides.

What we are going to do with our pentagon, is we are going to look at describing it.

In English, we use adjectives to describe, but with our shapes, we're going to look at some of our star words to make those descriptions.

And we're going to hopefully use our right angle detector or angle detector to help us identify those properties.

So let's complete this table all together.

The first column says, the first row even, sorry, says how the number of sides in this shape.

We can count the lines that make up the shape, the edges.

So one, two, three, four, five.

So I've completed my first box, this is a pentagon.

Next, I'm going to have a look at my shape, and see if I can find any right angles.

So here on the screen now, you can see my pentagon, but I also have a cutout of a Pentagon here.

And I'm going to use my right angle detector to make my way around the shape, to see if I can find any right angles.

So let's remember what a right angle looks like with my detector.

And then I'm going to have my shape, and put it into my angle detector.

So if I put that in there, oh wow, I can see that at the bottom, I have got one right angle.

If I move it this way, my angle detectors move, that's not a right angle.

It's much bigger.

And let me try this one.

That's much smaller.

And move round, oh again, I've got another angle, which is much bigger than a right angle.

And then the final corner, because that's my fifth one, I can see, well done, that it again it has got another right angle.

So if I go back to the screen, I should be able to see that it had two right angles.

If we continued, looking at our as we go round, I also mentioned that there were some angles, bigger and smaller than right angles.

Can you see any acute angles? On your finger can you show me how many acute angles you think you can see? Well done, if you said one.

I can see at the top here, the two lines joined together, but they are just smaller than a right angle.

So here is my acute angle.

So one acute angle, which means that the other two angles, which I said were more open when I did my example, are obtuse angles, angles bigger than a right angle.

So I can complete the table, and I have two obtuse angles.

If I look at my table, I should be able to do some maths to check that I've got the answer right.

If I add, the total amount of angles, so two right angles, one acute angle, two obtuse angles.

Two and one, and two, makes five.

That should be equal to the number of sides in my shape.

Cause last week when we did some learning, we investigated that the number of sides is always equal to the amount of angles inside that shape.

So I found my angles.

I've described my angles, well done.

Now we're going to have a look at finding a pair of parallel lines.

Remember, these are two lines that are opposite each other, that will never meet.

So if I get my pentagon back out, to investigate and you can do the same.

I'm going to have a look at these lines, and run my finger and extend my line to see if they would ever cross paths.

So I'm going to do my line going here, and if I do the opposite there, I can already see that the lines cross, they join to make a point, so they can't be parallel lines.

If I run my finger across the bottom of my pentagon, and down my sides and extend, I could see that they would cross paths further on, so they can't be parallel.

If I look at the two edges, the two sides, oh I can see that they make a right angle.

So that means that, the lines going upwards are turned but they're not moving in different directions.

And they're both running vertically.

And if I check, using my pentagon on the screen to extend those lines, I can see that if those lines continued, they would never meet.

So in my pentagon, I have one pair of parallel lines And perpendicular lines, those lines that join together to make a right angle.

I can already see that I have two right angles in my shape.

So.

Here, the two lines down the side going vertically, joined in with my horizontal line at the bottom, both make right angles.

And this means that that is a pair of perpendicular lines.

So I have one pair on this side and another pair on the other side.

So the number of pairs of perpendicular lines is two.

'Cause we're thinking about pairs.

When we look at the right angles, if a shape has a right angle, it must have that same amount of perpendicular lines.

So we've used our right angle detector to investigate this shape, find out all the different angles that helped us complete the table.

And then we looked at the shape, and use running our fingers along the sides and extending those lines to see if we would have any pairs of parallel lines.

What I would like you to do now is you are going to complete the same activity, but having a look at this quadrilateral on your screen now.

So you can pause the video.

I would like you to record your answers in your book.

I'm going to give you three minutes to complete this task, come back and we'll have a quick look at the answer.

So pause the video, now.

Amazing work, year three.

I can hear so many of your pencils working really hard, writing all of those answers down.

So let's quickly go through our answers now.

So, how many sides did our quadrilateral have? Well hopefully the name quadrilateral, reminded you that it must have four sides.

If you used your right angle detector to go around your shape, hopefully we would have found that there were two right angles in the shape.

Acute angles, so angles shorter, smaller, sorry, than a right angle.

We had one.

How many obtuse angles? That's greater than a right angle, we had one.

And so far that again adds up, two right angles, one acute, one obtuse, make our four sides, our four angles.

So we know that that's right.

Oh, parallel lines, so extending those lines.

Will they ever meet paths? Our top and our bottom lines are the same distance all the way across, so they will never meet.

If you had a look at the opposite two lines, then if we have a look here.

We can see that we've got an angle here, an acute angle, which is running inward.

So if it extended upwards, continued up, at some point it would meet the opposite side.

Okay, so it wasn't parallel.

So we only have one pair of parallel lines.

And if we look at the perpendicular lines, so this is when our right angles are created, we have two right angles.

So we must have two pairs of perpendicular lines.

Well done if you've got those answers correct.

If you want to mark them quickly pause the video, but we will be continuing as soon as possible.

Right, let's have a quick revision, 'cause I'm just hearing some of your answers, and I know that those parallel lines are really tricky.

So here, we've got two pictures on the screen, which explain our parallel lines.

Over here are two red lines.

We can see the arrows representing that they stayed the same distance apart all the way through.

Again on these two green lines, even if it's at a slight angle tilted to the side, if they are the same distance apart, all the way through, it is parallel.

We have a quick look here at our two orange lines.

As we move through two lines, we can see that the arrows between the distance between the two lines is getting shorter.

And if we extend those lines, that's what we were doing with our fingers.

Then we can see that eventually they will meet, so they are not parallel.

So quick recap on those, on that key word.

Right, let's move on, and have a look at our next learning, investigating this further.

So on your screen, you can see the shapes, A, B, and C.

This time, instead of trying to identify the different properties, we have been given the properties we are looking for in this table.

And we are going to try and find out which shape you can find those properties in.

If you're feeling brave and want to challenge yourself, then pause the video now, to see if you can work out the answer.

If you would like to go through this together, then continue watching this video.

So let's explore this one together.

So in my table, it says the property has two pairs of parallel lines.

All the angles are acute or has obtuse angles.

So let's have a look at this one to start with.

We're going to look at our first property.

Which of these shapes has two pairs of parallel lines.

So I've spread out my shapes a little bit because we're going to try and extend those lines to see if any of the sides will ever meet.

So if I look at A, and extend my lines, oh, I can see that they cross paths at different points.

This means that they are not parallel.

They don't stay the same distance apart.

If I look at B, I can see that the top and bottom line on my trapezium, they are equal distances apart at either end.

That's one pair of parallel lines.

If I do the same to the lines on the side, I can see.

At an angle which start to move towards each other.

I can see that if I continued that line even further, they would eventually meet.

So B only has one pair of parallel lines.

If I look at C, my rectangle.

Does it have any pairs of parallel lines? Well yes, each of the sides are equal distances apart.

So I have one set of parallel lines, and then two pairs of parallel lines.

So my answer, which shape has two pairs of parallel lines? Shout the answer.

The answer was.

Amazing, if you put the answer C well done.

So, that's the first bit of our table completed.

The next property, all the angles are acute, has obtuse angles.

So we're trying to identify the angles in the shapes now.

So let's work through this together by identifying all the angles in our shapes.

So if we look at A, we could even use our angle detector now, we can see that all the angles in A are acute.

They are smaller than a right angle.

If I look at B, I can see that here.

If I had my other line here, it would be a right angle.

This is going shorter, smaller than a right angle.

So we have an acute angle.

Here, we have an obtuse angle.

Sorry, my apologies, we have another acute angle.

Both of those lines are moving inwards.

At the top, we have an obtuse angle and another obtuse angle bigger than a right angle.

And in our shape C, we know that a rectangle has four right angles.

So I've successfully identified all the angles on my shapes.

If I have a look now at these descriptions, all the angles are acute.

Let's have a look at our shapes.

Can you see a shape that only has acute angles? Can you shout the letter of that shape for me now? Well done, if you said A, all of those angles are acute, smaller than a right angle.

And if we have a look at our next description, has obtuse angles.

Well, the rectangle only had right angles.

The triangle only had acute angles, and we can see in B we have two obtuse angles, and it was the only shape with obtuse angles.

Meaning that our final answer was B.

That was slightly different task, but still really important.

You've got lots of different things you can use to help you find these descriptions.

Your angle detector is going to be really important for trying to find the different sizes of your angles.

Using your finger to extend the lines, even if it's on a drawing, to see if the lines will ever meet will really help you with your parallel lines.

And remembering that right angles and perpendicular lines come together in a pair.

So what I would like you to do now, is you are going to have a go at completing your main independent tasks.

There are activities on there, just like we've done in our learning now.

So please pause the video, move onto the next activity to complete that in your exercise book or on your piece of paper, but come back to this video to have a look through our answers.

Brilliant, welcome back year three, you've worked so hard so far.

Let's have a quick look through our answers.

So part A, we had different shapes, and we had to do exactly what we did earlier by numbering the amount of these properties you could see in each of the shapes.

So if we have a look at A.

The number of sides, we had four sides.

We can see that there are zero right angles in our shape, there are.

two obtuse angles, greater than a right angle, and two acute angles.

So four angles altogether.

This is a parallelogram, and if we extend our lines, we have two pairs of parallel lines that the opposite sides will never meet.

So the answer pairs of parallel lines was two, and because there are no right angles in the shape, we don't have any pairs of perpendicular lines, so zero.

Shape B was a hexagon.

So first the number of sides, hexagon meaning it has six sides.

Again, we have no right angles.

If we looked really closely, we could see that all the angles in these shapes in this shape, were very open, meaning they are bigger than right angles.

What do we call angles bigger than right angles? Help me, shout it.

They are called.

Fantastic, they're called obtuse angles.

So I could see that in my hexagon, I had six obtuse angles.

So zero acute angles.

This next bit was really tricky.

Pairs of parallel lines.

Our hexagon actually has three different pairs of parallel lines.

The opposite sides, so this side and this side are parallel the same distance apart.

This edge and the opposite this edge, are the same distance apart so they are parallel.

And then this edge and it's opposite, this edge are also parallel.

So it had three pairs of parallel lines.

And again, no right angles, meaning no pairs of perpendicular lines, And our shape C.

We count the number of sides.

It has five sides, so it's an irregular Pentagon.

If I use my angle detector, I can see that there is one right angle.

If I go around the other angles to measure their sides, I can see that I have, I have only one acute angle, and I can also see that I have three obtuse angles, greater than our right angle.

In this shape, it was very tricky, there are no parallel lines.

If we extend any of the lines, they will meet.

We do have two edges that look like they might be parallel.

This one here and this edge here, but they're at slightly different angles.

Meaning eventually they would meet, if we continued those lines.

And finally it had one right angle.

So this line, and this line here join together to make one pair of perpendicular lines.

Well done.

Right, Part B, look at the shapes and complete the table.

There might be more than one answer, so be really careful here.

So the description has one right angle only.

The answer was F, can see it here.

Has more than four angles.

So this could be it had five, it had six angles.

The answers were D and E.

At least one angle is obtuse, it might've had more than one obtuse angle.

The answers were C, D, and E.

It has at least two angles are acute.

So it could either have had two or one angle as acute.

The answers were A, C, E, and F.

And finally it has at least one pair of perpendicular lines.

So those were the same ones that had right angles in.

The answers were B, D and F.

If you need to pause the video to mark your answers, that is absolutely fine, but we shall continue.

So some reasoning, this is really important, so that we're understanding, a greater level of understanding.

So Daisy says all triangles have the same type of angles.

Do you agree or disagree with Daisy, and use the triangles below to explain your answer? So if I have a look at my three triangles, and identify the different angles, I can see my green triangle, that there are acute angles.

I can even maybe see, is that an obtuse angle? We might have to investigate that further.

In my pink triangle, I can definitely see three acute angles.

But very clearly my yellow triangle, which is a right angle triangle, rather than our isosceles or equilateral triangles.

I can see that it has a right angle.

That means that all triangles don't have the same angles.

'Cause I can see a different angle, a right angle.

So hopefully you've written a lovely sentence, which might say something like this.

You should have said disagree with Daisy.

I disagree with Daisy because in one of the triangles, there is a right angle.

Most of the angles are acute, but this means that there are different types of angles depending on the type of triangle.

So our answer was disagree.

And then finally, so part C, our next question.

So write a sentence, using the star words, to describe the properties of the shapes.

What properties are always the same in triangles, and what properties might be different depending on the type of triangle? So we've got to think about all those properties from today.

Right angles, acute, obtuse, perpendicular, parallel, to see which were the same and which were different.

We're going to go back to this green triangle where I said we might have an obtuse angle at the top, greater than a right angle.

And yes, that is true.

Some triangles can have obtuse angles depending on how flat they are or squished.

I've given another example of this triangle where I've squished it a little bit further and we can, it's more clear here that our angle at the top is definitely obtuse.

So that was something to think about in our sentences.

So let's have a look at our perfect answer.

So what properties are always the same in triangles? So the properties that are always the same in triangles are that they always have three sides and three angles.

Also, there can never be any pairs of parallel lines because all the angles move inwards.

There can't be any parallel lines because all the lines connect and meet in a triangle.

So they were the three properties that are always the same in triangles, but the properties that might be different in triangles are the angle sizes.

That's what we just had a look at.

There can be a range of right angles, obtuse angles, and acute angles, but they are mainly acute.

And only in right angle triangles, will there be a pair of perpendicular lines.

In our isosceles and equilateral triangles because there's no right angles there are no perpendicular lines.

So that is a different description for each of our triangles.

So if you'd like to have a go at writing out that perfect answer to give yourself some practise, then pause the video to have a look through that now.

But let's continue and move on with the final parts of today's lesson.

So well done for your learning so far, to show me what you've learned, what I would like you to do is complete our final knowledge quiz.

So pause the video now to complete this.

Come back and we'll just finish off the final bits of today's learning.

Brilliant, thank you for doing your final knowledge quiz.

And it is just a huge goodbye from me.

Well done on today's learning! Hopefully we've become more confident in describing our properties of 2D shapes.

We'll see you back here for some exciting maths learning tomorrow.

If you've enjoyed today's lesson, or you would even like to show me some of your learning from today's lesson, then please ask a parent or an adult to post your work onto Twitter, using the hashtag that is on your screen now.

I'll make sure that I see that, but I can't wait to see you guys here again, for some more exciting learning! So goodbye.