Lesson video

Hello, everyone.

My name's Mrs. Kayleigh, and I'm really excited to be learning with you today.

So in today's lesson, we'll be using knowledge of addition facts within 10 to add within 20.

So let's have a look at today's lesson outcome.

Here's the outcome of today's lesson.

I can use knowledge of addition facts within 10 to add within 20.

I'm sure you know lots of addition facts within 10, and you can use these to help you work out addition facts within 20.

Here are the key words for today's lesson.

Can you say them after me? My turn, addition.

Your turn.

My turn, add, your turn.

My turn, plus, your turn.

These are all words that mean that we're going to add things together and we're going to use these in today's lesson.

So look out for them.

Here's today's lesson outline.

We're going to use knowledge of addition facts within 10 to add within 20, and we'll start off with some addition problems and then we'll be using a number line.

So let's start on the learning.

Here are some children that are going to help us today.

We've got Andeep and Izzy.

Andeep and Izzy have made some cakes.

First, they made 3 cakes, then they made 2 more.

How many have they made in total? Andeep said, "At first, we had 3 cakes." Can you see the 3 cakes in the tray? Izzy said, "Then we added 2 more." Can you see 2 more cakes are going to be added to the tray.

2 more than 3 is 5.

3 + 2 = 5.

Now we have 5 cakes.

Is that what you thought? So we know that 3 + 2 = 5.

So we can use this to help us with other additions.

Andeep and Izzy have made some buns.

First they made 13 buns, then they made 2 more.

How many have they made in total? So Andeep said, "At first, we had 13 buns." Can you see 13 buns on the tray? "Then we added 2 more." Can you see, they're going to put 2 more buns on the tray? 2 more than 13 is 15.

So 13 + 2 = 15.

Andeep said, "Now we have 15 buns." Andeep and Izzy have represented their cakes and buns on 10 frames.

Can you see at the top there we've got 3 + 2? That's the cakes that they made.

Then we've got 13 + 2, that's representing the buns.

Andeep said, "We had 3 + 2 cakes." Izzy said, "We had 13 + 2 buns." 3 + 2 = 5.

Can we use this to help us work out the next one? 13 + 2 = 15.

Can you see anything that's the same about those additions? Andeep said, "We can use 3 + 2 to help with 13 + 2." Izzy said, "I can see an extra 10." So can you see the extra 10 on the 10 frame there? So the rest of the cakes and the buns are the same, aren't they? 13 + 2 is 10 more than 3 + 2.

So 15 is 10 more than 5.

What do you notice here? Here we've got the cakes and the buns shown as an addition equation.

Andeep said, "They look similar." Izzy said, "We are adding 2 each time." Do you remember, there were 2 cakes added and 2 buns added? Andeep said, "3 + 2 = 5." Izzy said, "13 + 2 = 15." Can you see anything that's the same or different about those equations? Izzy said, "We can use 3 + 2 to help work out 13 + 2." Andeep has noticed that one of the parts is 10 more.

He's looking at the first number, the number that they started with.

So 13 is 10 more than 3.

Izzy has noticed that the sum or the total number of cakes or buns is 10 more.

So 15 is 10 more than 5.

Izzy has noticed that both sums end in 5.

So the ones digit is 5.

What do you notice here? We've got 13 + 2.

13 could be partitioned into 10 and 3.

So it's been partitioned into its tens and ones.

Izzy said, "We can add the ones together." I've put a purple circle around the ones.

Can you see? 3 + 2 = 5.

So 13 + 2 = 10 + 3 + 2.

13 + 2 is the same as 10 + 5.

13 + 2 = 15.

Andeep and Izzy need to buy some strawberries.

First they get 15 strawberries, then they get 3 more.

How many have they got now? So Andeep said, "At first, we had 15 strawberries." Can you see the 15 strawberries in the tray? Izzy said, "Then we added 3 more." I wonder how many they've got now.

Can you think of an addition fact that could help them work this out? Andeep said, "I know 5 + 3 = 8." So 3 more than 15 is 18.

So 15 + 3 = 18.

Is that what you thought? Andeep said, "Now we have 18 strawberries." What do you notice here? I can see the addition fact that they use to help them work this one out.

5 + 3 = 8.

That helped them to work out 15 + 3 = 18.

Can you see anything that's the same or different about these equations? Andeep said, "They look similar." Izzy has noticed that, "We are adding 3 each time." Andeep said, "5 + 3 = 8." And Izzy said, "15 + 3 = 18." We can use 5 + 3 to help work out 15 + 3.

One of the parts is 10 more.

So Andeep is looking at the first number that we started with.

15 is 10 more than 5.

Izzy said, "The sum is 10 more." So the total amount is 10 more.

18 is 10 more than 8.

Izzy has noticed that, "Both sums end in 8." So can you see the total amount, 8 and 18? They both end in 8.

So the ones digit is 8.

What do you notice here? We're going to work out 15 + 3.

We can partition 15 into its tens and ones.

15 is 10 and 5.

We can add the ones together.

So I've put a purple circle around the ones.

5 + 3 = 8.

Can we use this to help us work out 15 + 3? Yes.

15 + 3 = 10 + 5 + 3.

So 15 + 3 is the same as 10 + 8.

15 + 3 = 18.

Let's check your understanding.

Which part-part-whole model can help to solve 15 + 4? Now 15 + 4 is an addition fact within 20.

Can we use one of these addition facts within 10 to help us work it out? Pause the video while you think about this one.

Andeep and Izzy think the middle one will help.

5 + 4 will help to work out 15 + 4.

Izzy said, "5 + 4 is 9, so 15 + 4 is 19." Is that what you thought? Here's a task for you to have a go at.

Can you use the 10 frames to complete the additions? And which fact can you use to help and show it on the bottom 10 frames? And think about what do you notice.

So you are going to work out 15 + 4 for the first question and 14 + 5 for the second question.

And then see if you can think about which fact can help to work these out and show it on the bottom 10 frames.

Here's the second part of your task.

Can you use the 10 frames to solve the addition problems? The first problem says Izzy had 16 apples and picked 3 more.

How many has she got now? So you're going to work out 16 + 3, and think about which fact could you use to help.

Part b said Andeep had 17 cakes and made 2 more.

How many has he got now? So you're going to work out 17 + 2 and think about which fact could you use to help.

So pause the video and have a go at your tasks.

How did you get on with your tasks? Did you use the tens frames to show the additions? So first of all, we were working out 15 + 4 and this is equal 19.

Which fact can help? Andeep thinks that 5 + 4 = 9 and that's going to help him.

So 5 + 4 = 9 and 19 has 9 ones.

So both of those sums end in the number 9.

So the second one, we were working out 14 + 5 and that's equal to 19.

Izzy used the fact 4 + 5 = 9 to help her.

So can you see that both of the sums end in 9? The ones digit is 9.

Izzy has noticed that both of the questions had the same sum, 19.

So 15 + 4 = 14 + 5.

How did you get on with the second part of the task? Did you solve the addition problems? So in part a, Izzy had 16 apples and picked 3 more.

How many has she got now? So 16 + 3 = 19, and you could use the fact 6 + 3 = 9 to help.

In part B, Andeep had 17 cakes and made 2 more.

How many has he got now? It's 19.

17 + 2 = 19, and you could use the fact 7 + 2 = 9 to help you.

They both end in a 9, don't they? Let's move on to the second part of the lesson.

We'll be using a number line.

Here are 2 number lines.

The first number line is from zero to 10, and the second number line is from 10 to 20.

Can you see we've got two additions on these number lines.

The first one is an addition fact within 10, and the second one is an addition fact within 20.

What do you notice about them? Andeep has noticed that 3 + 2 = 5.

Izzy has noticed that 13 + 2 = 15.

Is there anything that's the same or different about these two? Andeep has noticed that they both end in 5.

So the sum is 5 and 15.

They both end in 5.

So the ones digit is 5.

Here we've got a stem sentence to help us, (hums) plus (hums) is equal to (hums).

So, (hums) plus (hums) is equal to (hums).

So we can use the addition facts within 10 to help us with the addition facts within 20.

3 + 2 = 5, so 13 + 2 = 15.

Let's put the numbers on the stem sentence.

3 + 2 = 5.

So 13 + 2 = 15.

What do you notice here? We've got two more additions here.

One of them is an addition within 10 and the other one is an addition within 20.

What do you notice? Andeep said, "8 + 2 = 10." Izzy said, "18 + 2 = 20." Is there anything that's the same or different about these two? Andeep has noticed they both end in zero, so the sum for the first one is 10 and for the second one is 20.

They both end in zero.

So the ones digit is zero.

Here we've got the stem sentence to help us.

We know that 8 + 2 = 10, so 18 + 2 = 20.

Let's put the numbers on the stem sentence.

Can you say it with me? 8 + 2 = 10.

So 18 + 2 = 20.

What do you notice here? Can you see we've got three number lines here? The first number line is from zero to 10, the second number line from 10 to 20, and the third number line is from 20 to 30.

Can you see I've put three additions on here? So we've got 8 + 2 = 10, 18 + 2 = 20, and 28 + 2 = 30.

What do you notice about those three additions? So each time we're adding 2, aren't we, to a number that ends in 8? And we end up with the sum that ends in zero.

So if we add 2 to a number ending in 8, will we always get a number ending in zero? What do you think? Izzy said, "Yes, the pattern will carry on." So even if we go up to larger numbers ending in 8, if we add 2, will we get a number that ends in zero? Let's check your understanding, who is correct? So Andeep said, "1 + 2 = 3." So 11 + 2 = 13.

Izzy said, "8 + 2 = 10, so 18 + 2 = 19." Now we've got some number lines here to help you.

Can you imagine the additions on the number line? Or you could try it on some number lines yourself.

So pause the video while you think about who is correct.

Who did you think was correct? So Andeep thought, "1 + 2 = 3, so 11 + 2 = 13." Yes, he's correct.

I can see on the number line that 1 + 2 = 3.

So 11 + 2 = 13.

Izzy thought, "8 + 2 = 10, so 18 + 2 = 19." Is she correct? No, I can see that 8 + 2 = 10, but 18 + 2 is not equal to 19.

It's equal to 20.

Is that what you thought? Let's check your understanding again.

Who do you agree with this time? Andeep said, "If we add 2 to a number with a ones digit of 3, we will get a number with a ones digit of 5." Izzy thinks, "If we add 2 to a number with a ones digit of 3, we will get a number with a ones digit of zero." Pause the video while you decide who you agree with, and perhaps you could try out on number line.

Who did you agree with here? So Andeep was correct.

If we add 2 to a number with a ones digit of 3, we will get a number with a ones digit of 5 because 2 + 3 = 5, Izzy was not correct.

If we add 2 to a number with a ones digit of 3, we won't get a number with a ones digit of zero.

So we know that 2 + 3 = 5, and this can be used for any addition where the ones are 2 and 3.

Here's a task for you to have a go at.

Can you show these additions on a number line and complete the stem sentence? So first of all, we've got an addition fact within 10, 2 + 6, and you can show that on the number line, and then you could use that to help you work out 12 + 6 and show that on the number line.

And can you put the numbers on the stem sentence? (hums) plus (hums) is equal to (hums).

So, (hums) plus (hums) is equal to (hums).

So we are thinking about our addition fact within 10 first and then using that to help us with our addition fact within 20.

Here's the second part of your task.

Can you show these additions on a number line and complete the stem sentence? So here we've got 6 + 4 and 16 + 4.

Can you show those on the number line and complete the stem sentence? Here's the third part of your task.

Can you solve these addition problems using a number line? So Andeep and Izzy have both got a problem to solve.

Andeep said, "I had 7 apples and then I picked 3 more.

How many have I got now? And you could show that on the first number line.

Then Izzy said I have 17 strawberries and then picked 3 more.

How many have I got now? And you could show that on the second number line.

And I wonder if you can use Andeep's question, the addition fact within 10, to help you work out Izzy's question, the number fact within 20.

And you can use the stem sentence to help you help you.

So pause the video while you have a go at your tasks.

How did you get on with your tasks? Did you show these additions on a number line? So first of all, we had 2 + 6 = 8, and I've shown that on the number line.

And then we had 12 + 6 = 18.

And I've shown that on the number line as well.

Can you see they look quite similar? So here's the stem sentence, 2 + 6 = 8.

So 12 + 6 = 18.

We can use the first one to help us work out the second one.

Here's the second part of your task.

Did you show these additions on a number line? So the first one was 6 + 4 = 10, and I've shown that on the number line.

The second 1 was 16 + 4 = 20.

Can you see they look quite similar? And here's the stem sentence, 6 + 4 = 10.

So 16 + 4 = 20.

Here's a third part of your task.

Did you solve the addition problems using a number line? So first of all, Andeep said, "I had 7 apples and then I pick 3 more.

How many have I got now?" And I've shown that on the first number line, 7 + 3 = 10.

Then we can use that to help us work out Izzy's question.

"I had 17 strawberries and then picked 3 more.

How many have I got now?" So 17 + 3 = 20.

Can you see they look quite similar? They both end in a zero.

So here's our stem sentence.

7 + 3 = 10.

So 17 + 3 = 20.

How did you get on with those? We've got to the end of our lesson today.

We've been using our knowledge of addition facts within 10 to add within 20.

And this is what we've learnt.

Addition facts within 10 can be applied to addition facts within 20.

For example, if 3 + 2 = 5, then 13 + 2 = 15.

A number line can be used to show the link between addition of one digit numbers and teen numbers.

And don't forget, you can use the stem sentence here.

If we add (hums) to a number with a ones digit of (hums), we will get a number with the ones digit of (hums).

And you can use this with larger numbers as well.

Well done, everyone.

See you next time.