Lesson video

Hello, my name is Dr.

Shorrack and I am excited to be learning with you.

You have made a great choice to learn maths with me today and I'm here to guide you through the learning.

Today's lesson is from the unit "Measuring Length and Recording in Tables".

This lesson is called Converting Between Metres and Centimetres.

As we move through the learning today, we are going to learn all about how we can measure in one unit and change it to another.

Sometimes learning can be a little bit tricky, especially when it's new, but I am here to guide you through the learning today.

And if we work really hard together, I know we can be successful.

These are the key words that we are gonna be using as we move through the learning today, we've got equivalent and we have convert.

So my turn, equivalent.

Your turn.

Brilliant, well done.

Let's just do that one more time.

My turn, equivalent.

Your turn, fantastic.

My turn, convert, your turn.

Fantastic, one more time.

Convert, your turn.

Fantastic, well done.

So those are the words to look out for as we move through the learning today.

We will be exploring what these keywords mean as we move through the learning today.

So today in our lesson about converting between metres and centimetres, we're going to look at how we convert between metres and centimetres and then we're gonna look at how we convert between metres and centimetres and just centimetres.

So we will start our learning by looking at how we convert between metres and centimetres.

In this lesson we've got Laura and Jacob who are going to help us progress through our learning.

So I'm going to show you this number line, have a look at it, maybe pause the video and tell someone what you notice.

What do you notice? That's right, Laura has noticed that 100 centimetres is equal to one metre.

Can you see how she has noticed that? Yes, if you look in the middle of our number line, we've got one metre on the top and 100 centimetres underneath it.

That means that 100 centimetres is equal to one metre.

They are the same length or height.

I wonder what Jacob's noticed? (person gasping) Jacob has noticed that 200 centimetres is equal to two metres.

Can you see that at the very end of our number line, we've got two metres and 200 centimetres.

They are both the same length and they both could be the same height.

So we can can use that relationship between one metre and 100 centimetres to help us convert between metres and centimetres.

And that means to help us change between metres and centimetres.

So I might give a reading in metres and I can change or convert it to centimetres.

So that relationship that Laura and Jacob noticed was that one metre is the same as 100 centimetres or two metres is the same as 200 centimetres.

So Laura is saying, well if one metre length is the same as 100 centimetres, then Jacob's saying, well two one metre length must be the same as 200 centimetres.

I wonder what you think might come next, what do you think Laura might notice? Has she spotted the pattern? If one one metre length is the same as 100 centimetres, then two one metre length must be the same as 200 centimetres.

That's right, and three one metre length must be the same as 300 centimetres.

Is that what you spotted? And here is a different scale.

What do you notice on this number line? Maybe pause the video, find someone and tell them what you notice about this number line.

Okay, what did you notice? Did you notice that 100 centimetres is equal to one metre and that there are 100 centimetres in one metre? And I'll show you a bar model to represent that one metre and 100 centimetres are the same value.

They are the same length and they are the same height and there are 100 centimetres in that one metre.

What does that mean? It means that centimetres must be quite a lot smaller 'cause you need 100 centimetres to be the same as one metre.

So one metre is equal to 100 centimetres.

I think we should practise that.

My turn, one metre is equal to 100 centimetres, your turn.

Fantastic, well done.

That's a really important number fact for you to learn.

And we can also use our other keyword.

One metre and 100 centimetres are equivalent and that means they are equal, they are the same, they're the same length as each other or the same height as each other.

So my term one metre and 100 centimetres are equivalent your term.

Fantastic, great learning so far today, I am really impressed.

So let's have a think about what we've learned so far.

One one metre is equivalent to 100 centimetres.

They are the same length or height.

And you can see that on my number line, got 100 centimetres and one metre are on the same point in that number line.

So one one metre is equivalent to 100 centimetres.

Ooh, so what have we got now? That's right.

Two one metres are equivalent to 200 centimetres.

Two metres is equal to 200 centimetres.

My turn, two metres is equal to 200 centimetres.

Your turn, fantastic.

I wonder if you might want to pause the video and tell someone what might come next.

That's right, did you get three metres are equal to 300 centimetres? Three one metre lengths are equivalent to 300 centimetres.

That means that four metres are equal to 400 centimetres or we could say 400 centimetres are equal to four metres.

What might come next? That's right.

Five metres are equal to 500 centimetres or we could say five one metre lengths are equivalent to 500 centimetres.

I wonder if you've spotted a pattern here at the moment.

Let's have a look at the top of the number line.

One metre, two metres, three metres, four metres, five metres.

Have you noticed that they are our counting numbers going in order.

So next it must be six metres.

We are counting in one metre length.

What about the bottom of the number line? 100 centimetres, 200 centimetres, 300 centimetres.

400 centimetres, 500 centimetres.

Oh, I wonder what might come next? That's right, we would have 600 centimetres and we are counting up in the bottom in 100 centimetres.

That's because we need 100 centimetres is the same as one metre.

So if the number line is going up by one metre on the top, then on the bottom it needs to go up by 100 centimetres because one metre is equal to 100 centimetres.

So we know next must be seven metres is 700 centimetres.

700 centimetres is equal to seven metres or seven one metre length is equivalent to 700 centimetres.

Eight one metre length are equivalent to 800 centimetres and nine one metre length are equivalent to 900 centimetres.

Some really key learning here.

This is you converting between metres and centimetres.

So if I said to you how many centimetres are equal to seven metres, what would you say? Can you use a number line to help you? That's right, seven metres are equal to 700 centimetres, 700 centimetres and seven metres are equivalent in length.

They're just different ways of describing that length.

You could say seven metres, you might say it's 700 centimetres.

So if I said how many centimetres are equivalent to three metres, what would you say? Fantastic, there are 300 centimetres in three metres.

300 centimetres are equivalent to three metres.

So if raw metre is 100 centimetres, what else do we know? We know all of these facts, don't we? We know if one metre is 100 centimetres, two metres must be equal to 200 centimetres, three metres must be equal to 300 centimetres, four metres must be equal to 400 centimetres.

I wonder if you can tell me a spot what comes next.

Maybe pause the video and find someone to tell.

Okay, what did you get? Did you get well five metres must be equal to 500 centimetres and six metres is equal to 600 centimetres.

Seven metres is equal to 700 centimetres, eight metres is equal to 800 centimetres and then nine metres is equal to 900 centimetres.

So this is us converting or changing between metres and centimetres.

I could say the height of a bush in my back garden is two metres but that would also be the same as 200 centimetres.

So we can measure the length or height of an object in metres or in centimetres and then we can vert between.

We can convert between them or change between them.

So I could measure the height of this tree in metres and then I could convert it and tell you what the height of that tree is in centimetres or the other way round.

But this time we're going to start with metres and we're going to find the height of this tree in metres and then we are gonna convert it or change it to centimetres using what we have just been learning.

So here is a representation of a tree in my garden and I've shown you roughly what that one metre would look like.

And Laura is saying well, before we measure we should estimate the height so we know whether our measurement is near.

I wonder if you would like to pause the video and using my guide of one metre, how many of those one metre length high do you think this tree is? So yes, how tall do you think this tree is? Well Jacob's saying he thinks the tree is about five metres tall.

So now we've estimated we can then measure it and then we will know if our measurement is correct or not because we have estimated it to be about five metres.

Oh look Jacob was right, the tree is actually five metres tall and I'm showing this in a bar model here.

My tree is five metres tall, that is the whole, and five metres is made up of five one metre lengths.

Five one metres is the same as five metres.

And you can see that in my bar model.

And we know that one metre is equal to 100 centimetres.

What does that mean? That's right, it means that those five one metre lengths are actually equal to five 100 centimetre lengths.

So five metres our whole is equal to five one metre lengths but also to five 100 centimetre lengths.

And what does that mean then? Well that means that five metres and 500 centimetres are equivalent.

Five metres is equal to 500 centimetres.

They are the same length or in this case the same height.

The tree is five metres tall.

But we could also say the tree is 500 centimetres tall.

They are the same height or length but we are just giving and saying them in different units.

So it's five metres or 500 centimetres.

Let's practise with those words.

So my turn, five metres and 500 centimetres are equivalent, your turn.

Fantastic, so now I'd like you just to have a look at this diagram and complete the sentence by converting the height of this house from metres into centimetres.

So you can notice the height of the house is seven metres and you have a sentence here, seven metres is equivalent to centimetres.

So using the learning so far, I wonder if you can complete that sentence, pause the video and when you have had chance to complete the sentence, press play.

Okay, so how did you get on? Did you work out that seven metres is equivalent to 700 centimetres? So my turn seven metres is equivalent to 700 centimetres, your turn.

Fantastic, well done.

And here's another one for you to have a go at.

True or false question.

Three metres is equivalent to 300 centimetres.

So do you think that's true or you think that's false? And once you've chosen, if you think that's true or false, I'd like you to choose one of my justifications.

So why do you say it's true or false? Is it because A, one metre is equivalent to 100 centimetres? So three metres is equivalent to 300 centimetres or is it B, 300 is a larger number than three.

So 300 centimetres must be larger than three metres.

So pause the video, tell me if it's true or false and choose your reason why and press play when you are ready.

Okay, should we have a look? Three metres is equivalent to 300 centimetres.

That's true, and why is it true? It's true because we have been learning that one metre is equivalent to 100 centimetres.

So three metres must be equivalent to 300 centimetres.

Okay, it's time for you to have a practise.

Your first task today I'd like you to convert these lengths between metres and centimetres.

And for your second task today I'd like you to put these objects in order of length shortest to longest.

So you've got A as a car, 400 centimetres.

B is a bicycle of two metres, C is the width of a door, 100 centimetres and D is the width of a bus.

Or sorry, the length of a bus at seven metres.

These are not to scale, not drawn to scale.

I wonder if you notice something.

It's always worthwhile in math stopping and thinking and noticing before you rush and start.

What have you noticed about the length? That's right, some of them are in centimetres and some of them are in metres.

So my hint to you would be to convert so that the measures are all in the same unit and that makes comparing and then putting things in order much easier.

And then your third task for today, I've got a problem for you.

A tree in the school playground is 900 centimetres tall.

The gardener cuts four metres off the tree.

What is the height of the tree? Now give your answer in centimetres and give your your answer in metres.

You might want to draw something to help you.

When you have finished all three tasks or sorry, pause the video and then when you have finished all three tasks, press play.

Okay, shall we see how you got on? So your first task was to convert these lengths between metres and centimetres.

Two metres is equal to 200 centimetres, four metres is equal to 400 centimetres, 600 centimetres is equal to six metres and 900 centimetres is equal to nine metres.

Got 300 centimetres is equal to three metres.

700 centimetres is equal to seven metres, eight metres is equal to 800 centimetres and five metres is equal to 500 centimetres.

Well done, for your second task, you are asked to put these objects in order of length shortest to longest.

Did you get this order, so that width of the door 100 centimetres, well, that's the same as one metre.

So that was the shortest of those lengths and the bicycle was two metres.

The car 400 centimetres and 400 centimetres is equal to four metres.

And then the bus was seven metres, well done.

And the problem that I gave you to solve about the tree in the school playground being 900 centimetres tall and the gardener cutting four metres off the tree.

And I asked you what was the height of the tree now and to give you ants in centimetres and in metres.

So I drew a bar model to help me.

So my whole tree was 900 centimetres and the gardener cut four metres off the tree.

Four metres is equal to 400 centimetres.

So then I could work out how much of the tree had been cut off, 900 centimetres subtract 400 centimetres is 500 centimetres.

So I knew that the height of the tree that was left was 500 centimetres.

The tree is now 500 centimetres tall.

But I asked you to give your answer in metres as well.

And we know 500 centimetres is equal to five metres.

Well done if you've got those correct.

Okay, time to move on to the second part of our learning today.

We're going to convert between metres and centimetres and just centimetres.

So got a quiz question for you.

Who do you think is correct? Laura is saying I am 140 centimetres tall and Jacob is saying, well I disagree, you are one metre and 40 centimetres tall.

So Laura's high is 140 centimetres but we are converting between just centimetres and metres in centimetres.

So now we're going to have a think about, what would Laura's height be if we did give that measurement in metres and centimetres.

Let's have a look at our number line, think about what you notice now.

We can see that one metre is the same as 100 centimetres and we can see Laura's height is just past that 100 centimetres.

So Laura's is 140 centimetres tall.

So we have another 40 centimetres to consider.

Laura is one metre which is the same as 100 centimetres and another 40 centimetres tall.

So Laura's height is one metre and 40 centimetres and that is equal to 140 centimetres.

So measurements can be converted between centimetres and whole metres and centimetres and we can use partitioning to help us.

So Laura's height is 140 centimetres, 140 is made up of 140.

So 140 centimetres is made up of 100 centimetres and 40 centimetres.

We know 100 centimetres is equal to one metre.

So 140 centimetres is equivalent to one metre and 40 centimetres.

140 centimetres is equal to one metre and 40 centimetres.

They are the same length or the same height as each other.

We can say it's 140 centimetres or we can say it's one metre 40 centimetres.

So let's revisit Laura and Jacob's conversation.

Who was correct? Yes, they were both correct because 140 centimetres is equivalent to one metres, 40 centimetres.

They were both correct 'cause they they use 140 centimetres and one metre 40 centimetres are the same.

So what do you think here, which line is longer? Is it line A, one metre and 60 centimetres or is it line B, 160 centimetres or are both lines the same length? Pause the video, tell someone what you think.

Okay, how did you get on? Did you go with C? Both lines are the same length because one metre and 60 centimetres is equivalent to 160 centimetres because one metre is equal to 100 centimetres.

Now Laura has been asked to measure the length of this bus and I've shown you what one metre is, how one metre is represented and Laura is always reminding us before we measure, we should estimate the length we know whether our measurement is near.

So how long do you think the bus is? Well Jacob's saying, I think the length of the bus will be about six metres and Laura measures the length of this bus in metres and centimetres and she finds out that it's six metres, 30 centimetres.

So Jacob's saying, well in centimetres the length of the bus must be 30 centimetres.

Do you think he's correct? Is the length of the bus 30 centimetres? and Laura is disagreeing.

I wonder why that might be.

Do you know why Laura is disagreeing? Is the length of the bus 30 centimetres? Ah, look, metres are made up from centimetres, so it must be more than 30 centimetres long because it's also six metres and six metres are made up of 600 centimetres.

So let's have a think about this conversation about the bus.

Measurements can be converted between metres and centimetres and just centimetres by partitioning.

So we've got six metres and 30 centimetres, well that's the same as six metres and another 30 centimetres.

And we know that one metre is equal to 100 centimetres.

So six metres is equal to 600 centimetres and we know then that six metres 30 centimetres is equivalent to 630 centimetres, six metres 30 centimetres equals 630 centimetres.

So the length of the bus was six metres, 30 centimetres or we could also say it was 630 centimetres.

So we can give measures in just metres, just centimetres or a mixture of both and we can convert and change between the different units.

Here we go.

Here's a question for you to check your understanding.

True or false, 206 centimetres is smaller than two metres, 60 centimetres.

Do you think that's true or do you think that's false? And then I'd like you to choose a reason for your answer.

Is it because 206 centimetres is equivalent to two metres, six centimetres, which is less than two metres, 60 centimetres? Or are you gonna go with B? 206 centimetres is equivalent to two metres and 60 centimetres.

So the symbol used should be an equal sign.

What do you think, pause the video and tell someone what you think.

Okay, should we have a look? Did you get that it's true? 206 centimetres is smaller than two metres 60.

But why? That's it because 206 is equivalent to two metres and six centimetres and that's less than two metres 60 centimetres.

We can use our understanding of converting between metres and centimetres to help us solve problems. So this relationship that we've been learning about, 10 10s, 100 centimetres and one metre.

So I'm going to work through one of these problems and I'm gonna let you have a go working through one.

So the question is, how many 10 centimetre lengths will we get if these ribbons are cut? So first of all we have to think what do we notice? That's right, the question's asking me about 10 centimetres but my ribbons are in metres so we need to convert so that we can have the measurements in the same unit and it makes things easier to solve.

So my ribbon is two metres long and two metres is equal to 200 centimetres and 200 is equal to 20 10s.

So if two metres is equal to 20 10 centimetre lengths, so we will have 20 10 centimetre lengths.

So I'm going to ask you to use my modelled structure to help you answer the same question about your piece of ribbon.

So how many 10 centimetre lengths will you get if your three metre ribbon is cut? Pause the video and then when you are ready, press play.

Okay, should we look how well you did? So did you notice that three metres is equal to 300 centimetres? 300 is equal to 30 10s.

So three metres is equal to 30 10 centimetre lengths.

So we will have 30 10 centimetre lengths.

So you have used your understanding of converting to help you solve the problem.

Let's have a look at these, what do you notice this time? That's it, the question is the same.

How many 10 centimetre lengths will we get if these ribbons are cut? But this time the numbers are not whole metres.

I've got 230 centimetres and I've given you 340 centimetres.

So watch me as I show you how to do this and then you'll be able to have a go on your own.

230 is made up of 200 and 30, 200 is equal to 20 10s and we have three more 10s, that's 23 10s.

So you'll get 23 10 centimetre lengths.

So pause the video, have a go on your own and when you are ready, press play.

Okay, should we see how you got on? So did you realise that 340 is made up of 300 and 40 and 300 is equal to 30 10s and you have four more tens, that's 34 10s, you're gonna have 34 10 centimetre length if you cut that piece of ribbon up, well done.

So I now it is your chance to have a practise.

I'd like you for task one to compare these lengths using greater than or smaller than or equal to.

For each equation, I'd like to give a reason for your answer.

So why did you choose greater than or less than or equal to? Your second task, I want you to choose which measurement is the odd one out and explain your choice.

Is it three metres, 40 centimetres? Is it 304 centimetres or is it 340 centimetres? And for your third task, I'd like to have a go at working out this problem.

A piece of ribbon is three metres, 60 long, 200 centimetres is cut from the ribbon.

What is the length of the ribbon now? I want you to check your answer by doing it in a different way.

When you finished all three tasks, press play.

Okay, should we see how well you did? So these are the answers and some reasons that you might have given.

So two metres, that's equal to 200 centimetres because one metre is equal to 100 centimetres.

So two metres is equal to 200 centimetres, 90 centimetres is less than nine metres because 90 centimetres is less than 100 centimetres.

So 90 centimetres is less than one metre.

So it's definitely less than nine metres.

340 centimetres is greater than three metres and four centimetres because 40 is bigger than four centimetres.

One metre is greater than 10 centimetres because one metre is the same as 100 centimetres and a hundred centimetres is definitely bigger than 10 centimetres.

And nine metres is greater than nine centimetres because metres are bigger than centimetres.

So they're both nines, but actually metres are bigger than centimetres.

And then one metre and three centimetres is equal to 103 centimetres because one metre is the same as 100 centimetres and then there are three more centimetres.

Which measurement is the odd one out? It's the middle one, 304 centimetres.

That's because the three metres 40 centimetres and 340 centimetres are equivalent.

They are the same.

304 centimetres is not the same measurement, that would be three metres and four centimetres.

And for the last task, the piece of ribbon, which was three metres 60 centimetres long and 200 centimetres was cut from it.

What was the length of it now? Well I bought bar model to help me.

So there's my length of my whole ribbon, three metres, 60 centimetres and I started by converting that to centimetres.

So three metres, 60 centimetres is equal to 360 centimetres.

I could then subtract the 200 to get 160 centimetres.

So the ribbon is 160 centimetres long.

And then I checked my answer by doing it in a different way.

I know that 200 centimetres is two metres and that's how much was cut off.

So three metres, 60 centimetres.

If I subtract the two metres, it is the same as one metre 60 centimetres long.

The ribbon is now one metre 60 centimetres long and we know that 160 centimetres is equal to one metre 60 centimetres.

So both methods gave me the same answer.

Fantastic learning today everybody on our lesson about converting between metres and centimetres.

I'm really impressed with how much progress you have made.

So to summarise, we now know that we can use the known facts that 100 centimetres are equivalent to one metre and can help and that can help us convert between centimetres and metres.

We can use partitioning and the relationship between one metre and 100 centimetres to help us convert between centimetres and metres and centimetres.

And we know it's always important to estimate so we know if our answer is near to the real value.

Well done today.