# Lesson video

In progress...

Hi everyone, how are you doing today? I'm Miss Mitchell, and today maths we're going to be estimating, measuring and comparing length in centimetres.

In today's lesson we will be estimating and measuring in centimetres.

You will then be comparing the objects in size, you will complete an independent task and then a quiz.

For today's lesson you will need, small objects of different size.

For example, a pen, a book, some pasta, a piece of paper.

You also need pencil and paper and a ruler.

Please make sure you ask your parent or carer before touching these items. So today we're going to be estimating, measuring and then Comparing.

What does the word estimating mean? Can you pause the video and tell me a definition of the word estimating.

Estimating is when you're making an educated guess or prediction.

You're making a judgement about something.

We're going to be measuring in centimetres today.

So we measure in centimetres when we are measuring smaller objects.

It is a standard unit of measure.

There are hundred centimetres in one metre.

And we know that we measure in metres for larger objects.

There are 100 centimetres in one metre.

When you are measuring, you need to make sure of a few things.

The first thing need to do, is to make sure whatever you're measuring is at the zero.

You always start at the zero.

What you don't want to do, is start at the end of the ruler or start on the number one.

You always start on the zero.

You need to make sure whatever you are measuring is straight against the ruler and there is no gap, you go to the end of what you're measuring.

And I can see that my line ends here, I go down to the ruler and I can read 20.

And this is in centimetres.

So my answer, the line would be 20 centimetres.

But instead of writing centimetres, we can just write cm.

20 centimetres, say 20 cm.

Here is the same line and the same ruler, but it has a different answer.

Which means this line has not been measured correctly.

Can you tell me why is this incorrect? What have I accidentally done wrong? That's right, I have started my line in the middle of the ruler.

And although it is straight, it is not starting at the number zero.

So this is incorrect because I have not started at zero, I've started in the middle of the ruler.

In today's lesson we're going to be estimating and measuring objects.

So, an object I have chosen to measure is my water bottle.

So the first thing I'm going to do is estimate the length.

Now looking at this water bottle, I think it's going to be around the length of a ruler, I think it's going to be about the same size of a ruler.

So I estimate that the water bottle is going to be maybe 28 centimetres, because I know it's about the same length as a 30 centimetre ruler.

So I think this water bottle is about 28 centimetres.

Now I've made my estimation, I need to now measure it with my ruler.

So I have my water bottle.

I'm going to line the zero up at the bottom, really carefully.

My ruler is straight against my object as much as it can be.

And I'm reading the top and I can say that my water bottle is 26 centimetres long.

So I was pretty close to my estimation.

So I estimated this was 28 centimetres, but it is 26 centimetres long.

I'm now going to have a go at estimating my TV control.

I think that this is going to be about half of a ruler, I think maybe a little bit smaller.

So maybe, 13 centimetres, about half.

So I've estimated, I'm now going to measure, so I make sure I start on my zero.

I make sure I start at the right end.

I don't want to start on the 30.

I line up, ooh, 14 centimetres.

So is really close.

14 centimetres is the length of this TV control.

So I estimated, I feel it was about 13 centimetres, but it is 14 centimetres.

So I've estimated and then I have measured.

I can now compare these two items, objects using my greater than and less than symbol, you know the crocodile.

So, my water bottle was, was it 26 centimetres, and this was 14.

So my water bottle is greater than my TV control and I can see that anyway.

So my water bottle is greater than my control and my control is less than my water bottle.

I will now show you the less than and greater than symbol now.

It is now time for you to have a go at the independent task.

So you're going to estimate the length of your object in centimetres.

And then you're going to measure it with a ruler.

Pause the video now.

Now remember, this is just an example.

So if you can, ask a parent or carer to check that yours are correct.

Well done for completing today's lesson.