Lesson video

Hello, my name's Mrs. Cornwell, and I'm going to be helping you with your learning today.

I'm so pleased we're working together.

I know you'll work really hard, and I think we're going to do brilliantly.

So let's get started.

Today's lesson is called Crossing the Tens Boundary Counting Forwards, and it comes from the unit Patterns in Counting from 20 to 100.

And so you are going to be looking for patterns in numbers that can help you today to cross that tens boundary.

And by the end of today's lesson, that should help you feel much more confident about counting forwards across that boundary up to 100.

So our keywords today, the words that will be important for our learning are tens boundary.

So my turn, tens boundary.

Your turn.

And decade number.

My turn, decade number.

Your turn.

Well done.

So in the first part of today's lesson, we are going to look at crossing the tens boundary counting forwards up to 50.

And then we'll move on in the second part of the lesson to counting up to 100 crossing that tens boundary.

In this lesson, you will meet Aisha and also Lucas.

They're going to be helping us with our learning today.

So here's Lucas and he's cut the rows off his 100 square, and he's placed them in a line.

Let's count the numbers we can see.

Are you ready? 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40.

Well done.

Lucas says, "I can see the decade numbers at the start of each decade." Can you see them there? 20, 30, 40.

Which numbers do you think will come after 40? Tap them on your Gattegno chart.

So we know, don't we, that the 20s numbers, 21, 22 comes after 20, and then 31, 32 comes after 30.

So after 40, what do we think will come? So we've got 40, 41, 42, 43, 44, 45, 46, 47, 48, 49.

That's right.

Well done.

The decade numbers come at the start of their decade on a number track.

So there you can see 20, 30, 40.

The numbers that follow the decade numbers start in the same way as that number, don't they? So we can see that there's 40, and then we can see 41, 42 all start with that 40, don't they? 41, 42, 43, 44, 45, 46, 47, 48, 49.

And that's the 40s decade.

What is different then about the decade numbers on a 100 square? So they don't look quite the same, do they? On a 100 square, the decade number is at the end of the row, isn't it? So instead of being at the start of the decade, it's at the end of the last decade.

So there we can see the decade numbers there.

And on a 100 square, after counting the decade number, you must go to the start of the next row to keep counting.

So there we can see 20.

But to find 21, we need to go to the start at the next row, don't we? There's 30 and there's 31 at the start of the next row.

The last number in the row on a 100 square changes to the next decade number, doesn't it? So we have a look here.

We've got the teens and after the teens is 20.

After the 20s is 30.

After the 30s is 40.

And after the 40s is, that's right, 50.

Well done.

Where the decade changes is called the tens boundary.

There's the 20s, there's the 30s.

I wonder where the tens boundary is.

That's right.

When counting, crossing the tens boundary can be difficult to remember because the pattern changes.

So it's where that pattern of counting changes.

The number begins in a different way because it's gone into a new decade.

So you can see we've gone from the 20s, 29 to 30, haven't we? Aisha and Lucas are tidying up the straws in the classroom.

Each bundle of straws is made up of 10 straws, and there are some extra straws as well.

How many straws have they collected? Lucas says, "I have two tens, which I know is 20." And Aisha says, "I have one one." They tap their numbers on Gattegno chart to help them say how many.

What numbers do you think they will tap? There's Lucas.

He says, "I will tap 20 to represent my two tens." And there it is on the Gattegno chart.

Aisha says, "I will tap one to represent one one." There that is as well.

So they tapped two tens one.

They tapped 21, didn't they? So that helped them to find what number they had, how many they had altogether.

Lucas and Aisha keep collecting straws.

Let's tap to represent the numbers they collect on your Gattegno chart.

So there we've got 21, 22, 23, 24, 25, 26, 27, 28, 29.

What number would we say after 29, I wonder? It may be hard to think of the number after 29 because you have to cross the tens boundary.

There's Lucas and he says, "When a number ends in nine, it is followed by a decade number." And Aisha tells us, "The next decade after the 20s is the 30s.

The next decade number after 29 must be 30.

Make sure you have some cubes, counters, or small objects grouped into tens with some extra ones as well.

So you might have some Lego or some blocks.

Get two tens and add on some extra ones until you reach nine ones.

So here's some Lego bricks.

And there we've got two tens and then nine extra ones.

Count another one.

What do you notice? That's right, it makes another 10, doesn't it? Nine and one more is 10.

So it makes another 10, So now you have three tens or 30.

You can count the numbers in a different way to help you understand that.

So there we've got 20, 9, and you can think of it as two tens nine.

Aisha says if I count one more, then nine will become 10.

So then I will have three tens, and that's what we just saw on the last slide, wasn't it? So there we've got two tens nine turns into three tens.

This row is from a 100 square.

Count along the row to find the missing decade number.

Count along the row starting with three tens one.

So there's three tens one, and then we've got three tens two, three tens three, three tens four, three tens five, three tens six, three tens seven, three tens eight, three tens nine.

"I know that after three tens nine, it must be four tens." And there it is, four tens, which is 40.

Now count along the decade starting with 31.

Are you ready? 31, 32, 33, 34, 35, 36, 37, 38, 39.

"I know that after 39, it must be 40." That's right.

You can also think of the patterns on a 100 square to help you, can't you? So there we can see the 30s, can't we? And we can see that pattern.

I know the 40s follow the 30s.

So 40 must come at the end of the 30s row.

There we go.

So now it's time to check your understanding.

So find the missing decade number.

So we've got a row from the 100 square there, and it says count along the row starting with four tens one.

So you need to start with four tens one and count along that row.

So pause the video now while you have a try at that.

So now let's try that together then.

So four tens one, four tens two, four tens three, four tens four, four tens five, four tens six, four tens seven, four tens eight, four tens nine, five tens.

Well done.

Now count along the row starting with 41.

So pause video again while you try that.

Okay, and now let's do it together.

41, 42, 43, 44, 45, 46, 47, 48, 49, 50.

Well done.

That was excellent.

So now another check.

Match the numbers that are the same, that represent the same amount.

So we've got four tens three, two tens four, and three tens four.

And on the other side we've got 24, 34, 43.

So pause the video now and you try and match those numbers up to the same, the number that represents the same amount.

Okay, now let's do it together.

So we've got four tens three.

We know four tens is 40, and we've got three extra ones, haven't we? So four tens three, we'll be the same as 43.

Two tens four, we've got two tens of 20 and an extra four.

So we've got 24.

And three tens four, well, three tens of 30 and an extra four will be, that's right, 34.

Now you know when the number ends in nine, it is always followed by a decade number.

There's some numbers ending in nine, 29, 39, 49.

Point to the number after 29.

That's right, it's 30.

And then point to the number after 39.

That's right, it's 40.

And point to the number after 49.

That's right, it's 50.

Well done.

We can think of the next row on the 100 square when we cross the tens boundary.

So if you were counting from 25, I wonder which decade we'd cross into.

You were counting the 20s.

So when you cross the tens boundary, you will count into the 30, that's right.

So let's try that.

25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36.

And you could keep going, couldn't you? Now let's count it in a different way.

Two tens five, two tens six, two tens seven, two tens eight, two tens nine, three tens.

That's right.

Three tens one, three tens two, three tens three, three tens four, three tens five, three tens six.

Excellent.

So now time to check your understanding again.

Start at three tens five and count on until you reach 50 or five tens, okay? So you're going to do that first.

So pause the video and start at three tens five and count up to five tens.

Okay, now let's do that together then.

So three tens five, three tens six, three tens seven, three tens eight, three tens nine, four tens.

Four tens one, four tens two, four tens three, four tens four, four tens five, four tens six, four tens seven, four tens eight, four tens nine, five tens.

Well done.

Then count the numbers in a different way.

So pause the video and start again.

And this time, you're counting from 35 up to 50.

Okay, and let's see how we got on.

Let's do that together.

So 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50.

Well done.

That was excellent counting.

Right, so here we've got Aisha, and she's looking at a 100 square.

And she's saying, "I think this is the 50s," looking at that row.

What mistake has been made? That's right.

You must look at the number at the start of the row, the start of the decade to name the row.

So 50 is at the end of the 40s row, isn't it? So this row is the 40s.

That's right.

So now your task for the first part of today's lesson is here.

It says cut the numbers from the strips below, then put them back in order.

Use your 100 square to help you if you need to.

Okay, so there's four strips, then you've got to cut each strip out.

When you found the first number in each strip, can you predict what the other numbers will be? So you can use the patterns that we've looked at to help you with that, can't you? So pause the video now while you have a try at the activity.

Okay, so how did you get on? So we can see the strips there.

And to help us to know where to start, we can think of what the first number is.

We know when we count forwards, the numbers become greater, so you can look for the smallest number, can't you? So let's have a look on that first strip.

We would start with 26, that's right.

Then it would go 27, 28, 29, 30.

Let's look at this second strip then.

Which number would we put first when counting forwards? That's right, we'd start with 27, then we'd go 28, 29, 30, 31.

What about the next strip? That's right, 28, 29, 30, 31, 32.

And then that last strip, where would we start? That's right, 29, 30, 31, 32, 33.

Did you notice that all of the numbers that ending nine are followed by a decade number? That's right.

Well done.

You've worked really hard in this first part of today's lesson.

Well done.

So the next part of the lesson then is crossing the tens boundary, but this time, counting all the way up to 100.

So here's Aisha and Lucas again, and they're tidying up the straws in the classroom.

Each bundle of straws is made up of 10 straws, and there are some extra straws.

So there's Lucas and he's saying, "I have five tens." Aisha keeps finding extra straws.

Count how many they find.

So there's five tens, and she says, "I will keep counting from five tens." So five tens one, five tens two, five tens three, five tens four, five tens five, five tens six, five tens seven, five tens eight, five tens nine.

Well done.

Now count them in a different way.

So this time instead of saying five tens, we're going to say 50 and count on from there.

So we've got 51, 52, 53, 54, 55, 56, 57, 58, 59.

Excellent counting.

What number will come after 59, I wonder? We can see 59 or five tens nine there, can't we? Aisha's helping and she says, "59 is five tens nine.

After nine, I need a new ten, and the next ten after five tens is six tens." So it must be six tens or 60.

Yes, well done.

What do you notice about the numbers marked on the number track here? That's right.

They all end in nine.

We've got 59, 69, 79.

What do you notice about the numbers that come after each of these numbers? That's right.

They're all decade numbers.

We've got 60, 70, and 80.

On a 100 square, the decade numbers still follow the numbers ending in nine.

So they look a bit different.

They're arrange in a different way, but the order of the counting is the same.

And we can see the numbers ending in nine there, and we can see that they're followed by the decade numbers.

So say the numbers that come after these numbers.

So 69, that's right, it will be 70.

79, it will be 80.

89, it will be 90.

And 99, It will be, that's right, 100.

And there's Aisha.

She says, "When a whole number ends in nine, it is always followed by a decade number." That's right.

So now time to check your understanding again.

Match the correct decade number to each row of the 100 square.

So you can see we've got three rows there, and you've got some decade numbers that come at the end of those rows.

So pause the video now while you match them up.

Right, now let's do that together then.

So that first row, what row is that? It is the 80s, isn't it? And what will come at the end of the 80s? So we know after the 80s, it is the 90s.

So after 89, it will be 90.

And the next row is, that's right, the 70s.

And after the 70s it comes the 80s.

So after 79, it will be 80.

That's right.

And then that next row is the 90s.

So after the 90s, it will be 100.

Fantastic.

So now we're going to count along the row starting with eight tens one to find the missing decade number because counting can help us count it.

So let's try that.

So we have got eight tens one, eight tens two, eight tens three, eight tens four, eight tens five, eight tens six, eight tens seven, eight tens eight, eight tens nine, nine tens, that's right.

89 ends in nine, so there must be a decade number next.

The 90s come after the 80s, it must be 90.

Now count again, starting with 81 this time.

So let's try together.

81, 82, 83, 84, 85, 86, 87, 88, 89, 90.

That's right.

So now it's time to check your understanding again.

So count along the row starting with nine tens one to find the missing decade number.

Okay, so we've got a row there, haven't we? And we're starting at nine tens one.

So pause the video while you try that.

Okay, and how did we do? Let's do it together.

Nine tens one, nine tens two, nine tens three, nine tens four, nine tens five, nine tens six, nine tens seven, nine tens eight, nine tens nine, ten tens, which we know is a 100, isn't it? That's right.

Now count again, starting with 91.

So pause video again while you count along starting at 91.

Okay, then let's do it together.

So we've got 91, 92, 93, 94, 95, 96, 97, 98, 99, 100.

Fantastic.

So now we've got a 100 square again, and we're going to count forward from these numbers, 57.

So I start my count at 57, and I count 57, 58, 59, 60, 61, 62.

And you could keep counting, couldn't you? Now let's start at 77.

I start my count at 77, and I count 77, 78, 79, 80, 81, 82.

Well done.

So let's check your understanding again.

So this time, you are going to count forward from 87.

So pause the video while you do that.

Make sure you keep counting till you've crossed that tens boundary.

Okay, and now let's try together.

So we've got 87.

I start my count at 87, and I count 87, 88, 89, 90, 91, 92.

You could keep counting all the way up to 100 if you wanted, couldn't you? Fantastic.

Here's Aisha again, and she's saying, "I am counting the straws.

I have counted up to seven tens nine.

What's the next number I say?" That's right.

When a whole number ends in nine, it is followed by a decade number.

The next decade after the 70s is the 80s, so it must be 80.

Here's Lucas.

He says, "I am counting the straws.

I have counted up to 89.

What is the next number I say?" That's right, when a whole number ends in nine, it is followed by a decade number.

The next decade after the 80s is the 90s, it must be 90.

So here's your task for the second part of today's lesson.

So we've got some more strips, haven't we, to cut out? And it says cut out each strip and then arrange them so that the numbers are in order.

Find the tens boundaries.

What is the same about them all? Okay, so pause the video while you try that now.

So let's go through it together then.

So you can see the strips.

You may have spread yours out in one long line, but I didn't have room for that.

So some of mine have gone underneath onto the next line, haven't they? But we can see the order here.

So we've got the 50s there, beginning with 51.

When you get to 59, you have to look for 60.

That's right.

And then you can see the row with 60 on, and it's got 70 at the end.

So then you have to look for, that's right, 71.

Okay, and then at the end of the 70s there, we've got 79.

So you need to look for 80, that's right.

And then at the end of the 80s, you've got 89, so you have to look for 90.

Well done.

Excellent.

You've worked really hard in today's lesson, haven't you? And found out lots about using patterns to help us with counting.

So let's think about what we've learned in today's lesson.

So we found out the numbers from zero to 100 have patterns that can help us to count across the tens boundary.

They are arranged differently on a number track and on a 100 square.

We can count the numbers in two ways.

We can say 21 or we can say two tens one, can't we? And when a whole number ends in nine, it is always followed by a decade number.

That's right.

Well done.

You've worked so hard today.

I've really enjoyed working with you.