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 are ready to work really hard and have lots of fun.

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

This lesson is called measure length using a ruler.

It is from the unit, number zero to 20 in different contexts.

By the end of this lesson, you will be able to use a ruler to measure length.

This is a really exciting lesson because I bet you've seen rulers all around you lots of times before, but you might have never learned how to use one correctly to be able to measure length.

So I am really excited about this lesson and I think by the end of it, you are going to be experts on how you can use a ruler to measure how long something is.

There are some key words that I would like you to practise so that you are ready for this lesson.

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

Ready? My turn, ruler, your turn.

My turn, centimetre, your turn.

My turn, centimetre, your turn.

My turn, zero, your turn.

Well done.

Did you notice that we said the same word twice? We said centimetre two times.

Even though you can only see the word centimetre on the board, right.

You can only see the word centimetre once.

We are going to learn about that in this lesson, so don't worry about it for now.

There are going to be two parts to this lesson.

To begin with, we're going to be thinking about what is a ruler for? And then in a little while, you're going to learn, how do you use a ruler? Let's start by thinking about what is a ruler for? There are two friends who are going to help us in this lesson.

Their names are Izzy and Jun.

Look out for them throughout the lesson because they have lots of helpful things to show you.

Izzy wants to measure the length of this pencil.

Jun says you could use centimetre cubes.

Let's see how she could do that.

One, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15.

Izzy says that is an accurate way to measure length, but it takes a long time.

You might have thought about this before.

Counting things one by one does take quite a long time, doesn't it? Perhaps there's a more efficient way that she could measure the length.

Jun says, you could use a 10 centimetre strip of paper like this.

If we know that is 10, we can start our count at 10 and we can say, 11, 12, 13, 14.

Oh dear, what happened? Izzy said, oh no, somebody accidentally bumped into me and all my cubes have moved.

I wonder if that's ever happened to you before when you are trying to measure something with cubes and you are trying really hard to get them in a nice straight line and then something accidentally bumps them and the cubes move and you have to start all over again.

Jun thinks that he knows something else that might help Izzy measure things in a bit of an easier way.

I wonder if you are thinking of the same thing as Jun.

Let's have a look.

You can measure length using a ruler.

You could use a ruler like this.

Have you got any rulers around you that you could have a look at? Rulers measure length in centimetres just like centimetre cubes.

Let's place the cubes along the ruler and count the centimetres.

One cube is one centimetre on the ruler, two cubes is two centimetres on the ruler, three cubes is three centimetres, four cubes is four centimetres, five cubes is five centimetres, six cubes is six centimetres, seven cubes is seven centimetres, eight cubes is eight centimetres, nine cubes is nine centimetres, 10 cubes is 10 centimetres, 11 cubes is 11 centimetres, 12 cubes is 12 centimetres, 13 cubes is 13 centimetres, 14 cubes is 14 centimetres, 15 cubes is 15 centimetres.

You can see that the centimetres on the cubes and the centimetres on the ruler are the same.

Izzy notice that there is one more number on the ruler that we haven't said yet.

Can you see which number it is? It's the zero, well done.

Jun says that rulers always start at zero.

If you have a ruler near you, see if you can find a zero on there.

Izzy said, I noticed some letters on the ruler too.

Can you see where the letters are? Well done, they're here.

The letters are cm.

Cm is a shorter way of writing centimetres.

Do you remember when we were practising our keywords? We said the word centimetres twice, didn't we? And one of those times, it's because we could see the letters cm.

It's a shorter way of writing centimetres.

I would like you to get a ruler of your own.

I want you to place your finger on the zero and practise counting up in centimetres.

I would like you to go all the way to the number 15.

So you're going to place your finger on the zero and you are going to start off like Jun, but I would like you to carry on, so you're going to say, one centimetre, two centimetres, three centimetres, all the way up to 15.

I wonder if you'd be able to go all the way back down to zero too.

Pause the video and have a go at counting in centimetres on your ruler.

Well done for some excellent counting.

When you want to use a ruler to measure the length of something, you can place the object that you want to measure next to the ruler like this.

The number at the end of the object tells you the length.

The end of this object, this pen is at the 12.

That means that this felt tip pen is 12 centimetres long.

If Izzy wants to measure the length of this pencil, she can place it along the ruler.

She knows the number at the end is going to tell her the length, so she's going to find the end of the pencil.

She can see that it's at the 14.

That means that this pencil is 14 centimetres long.

Let's check if you can do that.

How long do you think these objects are? Can you say your answers in centimetres? Pause the video and have a go at that now.

Let's see, how long do you think these objects are? The eraser is five centimetres long and the pen is 13 centimetres long.

Good job if you work those out correctly.

Now that you have learned about measuring length on a ruler, it is time for you to practise.

First, I would like you to look carefully at these pictures and write down the length of the pencil, the highlighter, and the felt tip.

When you've done that, I would like you to have a go at saying how tall each tower of blocks is.

Make sure you look carefully at the ruler that's next to each tower and give your answers in centimetres.

Are you ready to go and practise using a ruler to measure length? Off you go.

Let's have a look and see if you have been able to measure the length of these objects correctly.

So is 13 centimetres long? The highlighter is 10 centimetres long.

Now because that box is really small, you can't fit the whole word centimetres in there, can you? So you needed to use the shorter version by writing the the letters cm.

The felt tip is 15 centimetres long.

Well done if you measured those correctly.

Now let's have a look at the height of these towers.

The red tower of four bricks is 12 centimetres tall.

The yellow tower of five bricks is 11 centimetres tall and the blue tower of three bricks is 14 centimetres tall.

Well done if you were able to find the height of each tower correctly.

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

You are really going to be thinking about how do you use a ruler in this part of the lesson to make sure that you learn how to measure accurately.

There are some important things to remember when you use a ruler.

One thing is that you need to place your object as close to the ruler as possible.

This pen is not in a very helpful place at the moment for it to be measured.

You need to move the pen closer to the ruler like this.

Now that it's close to the ruler, you can see that this pen is 15 centimetres long.

Because this leaf is curved, it can't go right next to the ruler.

If the object you are measuring cannot be placed close to the ruler, you need to imagine straight lines at each end of the object pointing to the ruler.

A bit like this.

It's really important that you can see where the ends of your object are.

So if they can't be close to the ruler, you need to imagine some lines going straight down.

Now we can see that this leaf is eight centimetres long.

Let's see if you can do that.

Can you say the length of each of these objects in centimetres? They are not close to the ruler, so you will have to imagine some straight lines at each end of the object to help you to measure them.

Pause the video and have a go at finding the length of these objects.

Well done.

Let's see if you were able to imagine those straight lines in the right places.

If we start with the feather, we can see that one end of the feather is on the zero and the other end of the feather, lines up with 10.

So the feather is 10 centimetres long.

With the spoon, one end of the spoon lines up with zero and the other end is lined up with 14, so the spoon is 14 centimetres long.

Well done if you found the length of those objects.

We've just talked about placing the object as close to the ruler as you can and what to do if you can't place the object close to the ruler.

There is something else that's really important that you have to think about when you use a ruler.

You need to think about where you place the end of your object.

Izzy says, could you start right at the end of the ruler? Jun says, could you start wherever you want to? What do you think about where you should place the end of your object? Let's have a look.

When you use a ruler, you always start at zero.

So you have to line up one end of the object with the zero like this.

Can you see that Izzy has placed her highlighter so that one end lines up with the zero.

Jun says, I will ignore the space at the end of the ruler and line up with the zero like this.

Lots of rulers have a little space at the end before the zero.

You need to do what Jun says and ignore that space.

Make sure that you line your object up with the zero.

Now it's time for you to check that you can remember how to use a ruler to measure length.

Jun has tried to measure this feather, but there are some things that he could do to improve.

I would like you to pause the video and talk to a partner about how Jun could improve this measuring.

Do you notice anything that Jun might have forgotten to do? Pause the video and have a talk about that now.

Well done for thinking really carefully about how Jun has tried to measure this feather.

There are quite a few things that he could have done to improve his measuring.

Let's have a look at those now.

He forgot to place it as close to the ruler as he could.

So if he placed it like this, it would've been closer to the ruler and a bit easier to measure.

He also needed to place one end of the feather at zero.

He needed to move the feather along so that the start of the feather lined up with the zero.

It would also help Jun if he imagined some straight lines pointing to the ruler at each end of the feather like this.

Then he would be able to check that one end is lined up with zero and he would see that at the other end, it is lined up with 12.

Now Jun can see that this feather is 12 centimetres long.

Well done if you were able to help Jun improve his measuring.

Now that you've learned about some of the important things to remember about using a ruler to measure length, it is time for you to have a practise.

I would like you to have a look at how each object has been measured.

If you agree and you think that it's been measured correctly, I would like you to tick it.

And if you think that there's something wrong, I want you to explain what the mistake is to a partner.

When you've done that, I would like you to have a go at measuring some of your own objects.

You are going to choose three things that you would like to measure using a ruler.

You can draw it and write it like this, place it along your ruler.

Make sure that you line up one end with the zero and have a look to see how long the object is in centimetres and then at the bottom, you would write the length.

For this mini notebook, I would write, it was 10 centimetres long.

Now it's time for you to go and practise your measuring.

Off you go.

Well done, everyone.

Let's have a look at these first.

Which ones were correct and which ones have a mistake? The pen has been measured correctly.

It is 14 centimetres long.

The carrot has not been measured correctly and the spoon has not been measured correctly.

It's the same mistake in both.

The leaf has been measured correctly.

It is nine centimetres long.

So it's just the carrot and the spoon.

We can see they've both made the same mistake.

What do you think that mistake was? Well done if you said that the spoon and the carrot are not lined up with the zero.

They didn't start in the right place on the ruler.

Now let's have a look at what your measurements might have looked like for your own objects.

I measured the length of a pencil, it was 15 centimetres long.

I measured the length of a sharpener, it was three centimetres long.

I measured the length of a highlighter, it was 10 centimetres long.

Did you remember to place the start of your object on the zero on your ruler? Well done if you did.

That is really important when you measure length using a ruler.

Now that you are at the end of the lesson, you have learned that you can use a ruler to measure length in centimetres and you know that the letters cm, are a shorter way of writing the word, centimetres.

You know that when you use a ruler, you must always line up one end of the object with the zero.

You place the object as close to the ruler as you can.

And if the object can't be placed close to the ruler, you imagine those straight lines that are pointing to the ruler to help you line it up with zero and to find out the length of the object.

You have worked very hard in this lesson and done some really careful thinking about how to use a ruler.

Well done, everybody.

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

Bye, everyone.