Lesson video

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Hi everyone.

It's Miss Mitchell here.

Today in our math lesson, we are going to be measuring curved and straight lines.

In today's lesson, we'll be looking at measuring curved lines, straight lines in a shape.

You will then do an exploring task, and then a quiz.

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

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

For our Do Now, would you measure this in centimetres or metres? The length of a swimming pool.

The length of a pencil.

The length of an elephant.

The length of a rubber.

The length of a water bottle.

The height of a tree.

Pause the video to tell me the answers.

The length of a swimming pool you would measure in metres.

The length of a pencil.


The length of an elephant.


The length of a rubber.


The length of a water bottle.


And the height of a tree.


How did you get on? Here I have three lines.

I would like you to tell me which is the longest line and which is the shortest line.

So straightaway by looking at my lines, I can see that this is the longest line because it goes the furthest.

And I can that the second line is the shortest line because it goes the least furthest.

Quite straightforward.

Now which is the longest line? So one line is straight, and one line is curved.

So which line do you think is longer? And which line do you think is shorter? We don't know for certain but it looks like this straight line is going to be longer.

We don't know for sure but it looks like that, doesn't it? What about these two lines? Which is longer and which is shorter? Now, it's really hard to tell.

So how are you going to measure a curved line? Okay, so here I have a straight line and a curved line.

Now, I need to measure the length of this curved line.

Can I use a ruler to do this? Is it working? Not quite.

It's really difficult because it's curved.

So what you can do to measure a curved line is use some string.

So this is the type of string that I found in my home.

And what you do, you follow the line really carefully, with your fingers, and you put your finger at the point of where the line ends.

So my line ends here.

So from this, so from here, the end, this end, to here is the length of this line.

So then what I would do, I would get my ruler and I'd measure it from the beginning of the line to where my finger is.

And I can see that the curved line was 23 centimetres long.

So what I did is I used my fingers and carefully put, I put the beginning of the string at the beginning of the line.

I followed the string with the line really carefully, making sure the string was on the line as I went along, to get the full length.

And then I put my finger where the end is.

And then I measured the string against the ruler, and it's 23 centimetres long.

So that is how you measure a curved line.

Now we're going to measure straight lines in a shape.

So what shape is this called? This is called a triangle and it has three sides and three vertices.

Now, how would you measure the longest side? Could you please point to which you think is the longest side? That's right.

It would be this one up here.

So, to measure the longest side, you would have your ruler.

You would put the end of one side on the number zero, not at the end of the ruler, not on the number one.

So the end of one line carefully on the number zero.

You then line the ruler up against the line so it's nice and straight and there's no gap.

You then follow it to the end.

And you read the ruler where it says 17 centimetres.

So the length of this line is 17 centimetres long.

Remember, you don't need to write centimetres every time, you can just write cm.

And that stands for centimetres.

What shape is this? Measure its longest side.

Now, what shape is this? It is a rectangle.

So which side am I going to measure? I'm going to measure this side down here.

Now, why aren't I measuring this side up here? Why am I measuring this one? That's right, it doesn't matter.

These opposite sides are equal in length.

So I just need to measure one of them and I will know the length of the other.

So again, you line up the shape on the zero, not on the end, not on the one.

You line up the ruler so it's against the line.

You go to the end of the shape, or the end of the line, and you read it says 23 centimetres.

So that's 23 cm, 23 centimetres.

Let's try one more.

What shape is this? This is a trapezium.

Now, which side is the longest? That would be this line down here.

So again, you line up one end on the zero.

You have the ruler against the line, nice and straight, no gap.

You follow it to the end where you can read the number off the ruler.

And the number is 18 centimetres.

Now remember, make sure you're starting at the zero and not on the 30.

You are now going to explore.

I would like you to draw six 2-D shapes with straight lines and then measure its longest side with a ruler.

For an extension task, could you also draw some curved lines and have a go at measuring those with string? If you're not sure, ask a parent or carer to check that you're on the right track.

Well done for today.

You worked really hard and I'd love to see your work.

If you'd like to share your work with Oak National, please ask your parent or carer to share your work on Twitter tagging @OakNational and hashtag LearnwithOak.

You've worked really hard.

Now let's see what you remember by completing the quiz.

Well done for today.