# Lesson video

In progress...

Hi, everyone.

How are you? I'm Miss Mitchell.

It's the last lesson in our unit, so today, we're going to be consolidating and reviewing length.

In today's lesson, we will be consolidating and reviewing length.

We will then complete a quiz.

For today's lesson, you will need a pencil, some paper, and a ruler.

Pause the video now to get this if you have not got it already.

What I would like you to do, I would like you to read these and tell me whether they should be measured in metres or centimetres.

The length of a classroom, the length of your foot, the length of a road, the length of a DVD, and the length of your ear.

Pause the video and tell me whether they should be measured in centimetres or metres.

The length of a classroom will be measured in metres.

Length of a DVD, centimetres.

We know that we measure smaller things in centimetres and larger things in metres.

The length of the school hall is about two metres.

Do you think that's true or do you think that's false? The length of a school hall is about two metres.

The length of a laptop is about three metres.

Do you think that's true or do you think that's false? The length of a book is about 20 centimetres.

The length of your ear is more than 20 centimetres.

Pause the video to tell me whether these are true or false.

The length of the school hall is about two metres.

False, it will be much greater than that.

The length of a laptop is about three metres.

False, it will be smaller than that.

The length of a book is about 20 centimetres.

True, depending on the book, but generally about that.

The length of your ear is more than 20 centimetres.

False, your ear will be smaller than that.

Can you tell me how many centimetres are in a metre? How many centimetres are in a metre? There are 100 centimetres in one metre.

Well done if you got that correct.

Looking at the ruler, could you please tell me how long the line is.

How long is the line? The line is 16 centimetres long.

I start the line at the zero, I follow the line all along until it stops, I follow it down, it says 16 centimetres.

Remember, you don't have to write centimetres, you can just write C-M, which stands for centimetres.

What is the length of this line here? What is the length of this line? The length of this line is 11 centimetres.

Again, you start on the zero, you don't start at the beginning of the ruler, and you don't start on the one, and you follow the line to the end, it ends here, you go down to 11, so you know the line is 11 centimetres long.

Which line is the longest? Which line is the shortest? How could we find out the length of this line? This curved line is longer than this straight line.

But how can we find out the length of a curved line that isn't straight? We can't use a ruler.

What could we do? To measure a curved line, you can use a piece of string.

You would use a piece of string to follow the curved line.

You would maybe cut the string to when the line ends and then you can hold the string up against the piece of ruler, sorry, you can hold the piece of string against the ruler, nice and straight, and then measure the length of the string.

The length of the string will tell you the length of the curved line.

That is how you find out the length of a wiggly or curved line.

Measure the longest side of this shape.

What shape is this? This is a triangle.

Which side do you think is the longest? It will be this line here.

To measure the length of the longest side, you line the zero up at one side.

The ruler goes right against the line so there's no gap.

You follow the line down, all the way to the end where it says 15 centimetres.

You know that the longest side is 15 centimetres.

I would like to draw another line that is four centimetres shorter than 15 centimetres.

Could you pause the video and can you draw a line that is four centimetres shorter than 15 centimetres? To work this out, you would do 15 take away four, which is equal to 11.

Did you draw a line that was 11 centimetres long? If you're not sure, please ask a parent or carer to check your work.

I would like to draw another line that is three centimetres longer than five centimetres.

Could you draw a line that is three centimetres longer than five centimetres? Pause the video now to do this.

To work that out, I would do five centimetres plus three centimetres, which is equal to eight centimetres.

Now check your line is eight centimetres long and if you're not sure, ask a parent or carer to check your work.

Let's try a word problem.

Joe's arm is 21 centimetres long and Amie's arm is 26 centimetres long.

What is the total length of both of their arms? To work this out, I need to work out the whole and I know two parts.

Joe's arm is 21 centimetres long and Amie's arm is 26 centimetres long.

We need to work out the whole, which is the total length.

To work it out, I would do 21 plus 26 is equal to the unknown.

I can then use my Baum model, which has helped me form my equation to help me now solve my equation.

21 plus 26 is equal to 47.

The total length is 47 centimetres long.

Let's try a new word problem.

Tony has a piece of ribbon measuring 57 centimetres.

He cut off 20 centimetres.

Then, he cut off another 11.

How long is the ribbon now? What do we know and what is unknown? We know that he started with 57 centimetres of ribbon and we know he then cut 20 centimetres off.

We also know he cut another 11 centimetres off.

But we don't know how much is left, how much there is now.

What equation would I use to solve this? Look at my Baum model to help me.

57 take away 20 take away 11 is equal to the unknown.

I can now solve my equation.

57 take away 20 take away 11 is equal to 26.

That's 26 centimetres.

Well done for your work today.

You've done a really great job.