Lesson video

Welcome back to your year five math lessons.

I'm Mr. Barton, I'm going to be working with you today.

Last lesson, I taught you the way that I remember eight multiply by eight is equal to 64 by humming the 64 zillion lane theme tune to myself.

I thought I'd share another city rhyme with you today for seven multiplied by seven.

I always start with seven sevens, are equal to 49 or wakey wakey rise and shine seven sevens are 49.

Again, another city rhyme but it helps me remember and that's all that really matters.

This is your third lesson in your unit on volume.

Today's lesson objective is to estimate the volume of objects.

This estimate requires lesson one and lesson two to be have been completed so that you know what we're talking about.

So if you haven't done that go and do that now.

Make sure you've done the pre-lesson quiz and make sure that you're ready to work.

That you've got your pencil and paper and that you're free from distractions.

Are you ready? Let's get going.

Our learning so far.

In lesson one, we defined volume as the amount of space taken up by an object.

We also mentioned that volume is measured in cubic units.

In lesson two, we started to explore cube to numbers and we found that when we multiply the same factor three times, we get a cubed number.

It's called a cubed number cause if we draw it out, it creates a cube.

It's three dimensional.

It has a height, it has a width and it has that length.

So it's three dimensional and that's going to be really key for today's learning.

Here we have pictorial representations of cubed numbers, which one of them do you think, which one of them do you think shows us one cubed unit? Why does it show us one cubed unit? Write down your answer now.

Good if you picked this one, you were correct.

Let's investigate a little bit further.

Now I've made that image slightly bigger.

What's on your screen now is not to scale.

It's a representation to help us learn, but here's my cube.

It's one centimetre in length, it's height is one centimetre and its width is one centimetre.

One centimetre times one centimetre times one centimetre is equal to one centimetre cubed or one cubed if we were going to write it in a shortened version.

This one centimetre cubed unit is what we can use to help us measure volume because when we're measuring volume we're measuring the amount of space that something takes up.

The centimetre cubed is 3D it is not 2D.

The volume of this one centimetre cubed is 3D even though on your page it looks 2D.

Remember it's not to scale I've made it much larger for us to work with.

I'm now going to shrink that representation down a little.

If each cube has the volume of one centimetre cubed, what is the volume of the following shapes? Pause your video.

You should have found that each of the shapes has a volume of four centimetres cubed.

Each one of them are made up of our centimetre cube four times.

The reason it's cubed is because each of our shapes are 3D and they have three dimensions.

For example this one has a dimension of one for its a width, one for its length and four for its heights.

One times one is still one, one times four is equal to four and we are dealing with centimetres cubed.

Similarly the second one has a height of two centimetres cubed or centimetres a width of one and a length of two.

Two multiplied by one is equal to two and then two multiply by two is equal to four centimetres cubed cause it exists in three dimensions.

Let's have a look at a real life example now.

Here I'm about to measure my whiteboard rubber.

My whiteboard rubber is three dimensional.

It's a cuboid.

It has a height a width and a length.

And I'm going to start by measuring its width.

I'm using my ones deans.

Now these deans or these cubes are one centimetre by one centimetre by one centimetre.

They're one centimetre cubed.

So forever use deans or ten of ones at school that's what we're using as our reference points.

We can see therefore that the width of this rubber is equal to eight centimetres.

We've also could use a ruler to measure that but I like to think about how many of these are fitting in there.

I'm now going to measure the length.

I use my centimetres cubed again but we could use our ruler just to measure the length.

I found that the length of my rubber is equal to five centimetres.

Finally, we need to do the height.

Now this is quite hard on a video, so I'm going to to rotate my rubber.

So I'm doing this part here it's the height.

If I rotate it you can see it more clearly we've got one and two the height is two centimetres, two of our cubed units centimetre cubed units.

Just going to show you again our height if I build up two is the same as the one underneath.

I now need to multiply my dimensions together cause I've only found one strip of each the width multiplied by the length multiplied by the height.

I start by finding the easiest ones to multiply five to multiply by two is 10.

So then I do eight multiply by 10 is 80.

The volume of my shape is 80 centimetres cubed.

Here are some objects that you will find around your house a pencil, a book it could be a reading book or an exercise book and a DVD or a games case.

I'd like you to pause the video in a second and estimate how many of our centimetre cubed units fit into one of these? You'll start by thinking about the length then the width and then the height.

For example I estimate that my pencil will be 12 centimetres cubed because it isn't very tooler wide probably about one but it is quite long.

Pause your video now and estimate each of those items. Right then let's have a look.

We're going to do the pencil and the book.

Now your pencil or your book may have been a different length or height or width to mine and that's okay.

This is just to show you how we're doing it.

So here we have my pencil.

Now I'm going to use a tens Dean to speed it up so you're not waiting the whole time.

My tens Dane is made up of 10 one centimetre cubes.

So I know that the tens Dean is equal to 10 centimetres.

Now you're going to see that there's actually a little bit of my pencil left.

We're doing approximately here I'm not too worried about it being absolutely perfect but we're just understanding space.

So there we have the length of my pencil is equal to 17 centimetres 10 and seven.

I'm now going to do the width.

Now my pencil is not very wide at all.

If I can know the bit that's sharpened and just looking at the pencil it's about one centimetre and the heights if I compare them I can see that actually is less than one centimetre but for now we're going to do approximates.

So the height is approximately one centimetre if I put that back where it should be that would be good.

So I do my length times the width times the height and this is going to be an approximate cause as we saw the pencil wasn't quite tall enough but it was a bit longer.

17 times one is equal to one 17 times a one again is equal to 17 and our units is centimetres cubed because we're measuring cubed units.

So a pencil is approximately 17 centimetres cubed and finally let's have a look at our book.

Now remember your book may be a different size to mine.

It maybe a different thickness or a different height.

I'm using my tens Dean again to represent 10 ones again it's about 10 centimetres.

So I can see that my width is equal to 15 centimetres.

And we're going to repeat this with the length.

Now my length is slightly bigger or longer.

So I've got two 10 centimetres and two one centimetres.

So my length is equal to 22 centimetres.

And again the height's quite tricky to show you but in this example the height is equal to one centimetre.

Your book might be thicker especially if it's a reading book you might have two centimetres, three centimetres, maybe up to five centimetres there If it's quite a long book the height is one centimetre.

I now need to multiply these together the width times the length times the height cause we've only found the ones.

So we're finding 15 multiplied by 22 multiplied by one, let's start with 15 multiply by 22, 15 multiply by 20 is equal to 300, 15 multiplied by two is equal 30.

I add those together to make 330.

I then do 330 multiplied by one to get me 330 centimetres cubed because 330 of my cubed centimetres would fit into that book.

The book takes up 330 centimetres cubed.

It's time for your independent task now.

I'd like you to match the objects to their estimated volume and they're all in centimetres cubed.

Then I'd like you to put them in order starting with the greatest volume.

When I was doing this task I use the idea that my pencil was approximately 20 centimetres cubed.

Actually the one I've just done was 17 centimetres cubed.

If you have any of these objects at home you might even want to measure their length to see if that gives you any hints.

Remember you are thinking about real life objects not the pictures and none of the pictures on the screen are to scale especially the pencil and especially the concrete mixing truck.

I'd like you to pause your video now and have a go at matching the images to the estimated volume and then put them in order.

Pause your video? And here are your answers.

Well done for completing today's lesson don't forget to come back for the next lesson so that we can really challenge you and don't get to complete your end of lesson quiz.

Well done.