Lesson video

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

Now, today we're going to be finding out all about two-digit numbers.

We're going to be looking very carefully, thinking about what we notice, looking for any patterns that can help us so we can use things that we already know to help us with new learning.

So I'm really looking forward to working with you today.

I know you're going to work really hard and wIll do really well.

So let's get started.

Our lesson today is called Count a Large Group of Objects by Counting Tens and Ones, and it comes from the units counting and representing numbers from 20 to 99.

So in our lesson, we're going to count larger groups of objects efficiently.

So grouping ones into tens and then counting the extra ones to help us.

And by the end of our lesson, you should feel really confident with counting larger groups of objects in a quick and efficient way.

So our keyword today is unitizing.

My turn, unitizing.

Your turn.

Well done.

So the first part of our lesson is called counting efficiently using tens and ones.

And in this lesson, you'll meet Andeep and also Laura.

So Laura is counting her money.

You can see she's got some 10 p coins and some one p coins.

Let's count the tens and ones to see how much money she has.

"I know 10 p represents ten one pennies," she says.

Each 10 p is one group of 10.

We have mm groups of 10 and mm more ones.

We have five groups of 10, that's right.

And four more ones.

So in our place value chart, we'll write five in the tens to represent the five tens and then the four ones.

How many ones do we have altogether then? We have mm ones.

So Laura says, "I can't separate the ones to count them." So we know each 10 p coin is the same as ten one pennies, but we can't separate the 10 p's can we? We know that one 10 is the same as 10 ones.

So five tens will be the same as 50 ones, won't it? So we have 54 ones.

Fifty-four, that's how we write it in words, isn't it? When we use one item to represent several other items, it is called unitizing.

We know one 10 p is the same as 10 one p coins, even though we can't separate the ones to count them.

So we can see the tokens there with the 10 spots remind us of the ten one pennies.

Counting in ones would take a long time and we could miscount.

Unitizing helps us to count more efficiently.

We can use it to help us count the tens, and we would say 10 p, 20 p, 30 p.

Andeep counts his coins.

10 p is one group of 10, so I can count them in tens.

10, 20, 30, 40, 50.

I have 50 p.

Do you agree with Andeep? Has he got 50 P there? He's got five coins, hasn't he? Laura's helping us here.

She says the 10 p coins can be counted in tens, but the one p coins must be counted in ones, mustn't they? So 10 p, 20 p, 30 p, 31 p, 32 p.

And then when we write that in our place value chart, we know that the 30 p can be represented by three, meaning three tens.

And then we have two more ones as well, don't we? So now it's time to check your understanding.

There are four groups of 10 and three ones.

How many ones are there all together? And we can see the coins there.

Can't we? Four tens and three ones.

So is it A, seven ones, B, 43 ones, or C, 34 ones? So pause the video now while you have a think about that.

Okay, and let's see how you got on then.

What did you think? That's right.

It will be 43 ones, won't it? So we count in tens until there are no more tens.

Then we count on in ones.

10 p, 20 p, 30 p, 40 p, and then we go 41 p, 42 p, 43 p.

And there if we put it on a place value chart, we can see that we've got 40 p, which is 4 tens, and then we have three more ones.

So here's what a 100 square and this 100 square has darker lines to help you see five ones and five tens.

Andy arranges the stick as he has collected on the 100 square.

"I think this makes him easier to count.

I can use the rows of 10 to help me," he says.

10, 20, 30, 40, 50.

So you can count the rows of 10, can't you? I have five tens, which is 50.

I can use the darker line at the midpoint to see that I have six ones.

So if you see the line going down, we know that it splits each group of 10 into two fives, doesn't it? So we can see that we've got a five and then we've got an extra one, so it should be six ones.

And Andeep says I will prove it by counting on from 50 in one.

So we've got 50 there, 51, 52, 53, 54, 55, 56.

There are five tens and six ones.

If we counted them again in ones, how many stickers would Andeep have? Hmm.

So let's have a think.

We've got five tens and we've got six ones.

So that's right.

Altogether that number would be 56, wouldn't it? 56 ones.

Laura decides to arrange the base 10 blocks on her 100 square.

"I will be able to count the tens and ones so I can count efficiently," she says.

10, 20, 30, 40, 41, 42, 43, 44, 45, 46, 47, 48.

"I have four tens and eight more ones," she says.

So if we put that in a place value chart, we would have four would represent the four tens, that goes in the tens column, and then eight more ones to represent those eight extra ones.

I have 48 ones all together.

If you counted each cube in ones, we would have 48, wouldn't we? So now it's time to check your understanding again.

Andeep collects some base 10 blocks and put some on his 100 square.

Complete the stem sentences to find out how many he has altogether.

So we have mm groups of 10 and mm more ones.

We have mm ones.

So pause video now while you try that.

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

So we have six groups of 10, don't we? Did you count each row of 10? And then we have four more ones.

And you may have counted on in ones there, or you may have used that darker line, the midpoint to see that it's one less than the five, isn't it? So it must be four.

So how many ones would there be altogether then? We've got six groups of 10 and four more ones.

So that would be six tens and four ones.

We would have 10, 20, 30, 40, 50, 60, 61, 62, 63, 64.

So we have 64 ones altogether because we know each group of 10 contains 10 ones, doesn't it? So now here's the task for the first part of our lesson.

Play a matching game, cut out the cards, and match the cards that have the same value.

So we've got some 100 squares with some tens and ones on there and you've got to match it to the number represented in tens and ones in words and in digits.

So you could use base 10 blocks on a 100 square to help you.

Couldn't you? Remember to count each 10 block in tens and then count on in ones.

So pause the video now while you try that.

Did you do this? So we can see here there's two rows of 10 and then eight ones, aren't there? So we've got two tens and eight ones, which is the same as 28 or there it is represented in digits.

Then here we've got eight tens, haven't we? And two extra ones, two more ones.

And then that's 82 written in words or there it is in digits.

And then we've got four tens and five ones there.

And we can see that's 45, isn't it? Or we can represent 45 in digits like that, 45 ones.

And then we've got five tens and four ones there, which is the same as 54.

And there it is in digits.

So 54 ones.

And then the next part of the activity, we've got three tens and six ones there we can see, which is the same as 36.

And there it is in digits.

And then here you may have used the darker lines to help you here.

You may have said right, I can see the darker line going across the 100 square.

So that's half of 100, isn't it? That's 50.

And so there's one more 10 there, 60.

And then we can see there's three more ones there.

So that's six tens and three ones.

And then that's the same as 63 or there it is in digits.

And then here we've got seven tens and nine ones, 79, or 79 written in digits there.

And then we've got nine tens and seven ones.

You may have looked and thought, oh, it's only three less than the complete 100 square.

So three less than 100 would be 97, and there it is in digits.

So well done if you did that.

Okay, so here's the second part of our lesson then, and it's called understanding place value with tens and ones.

So Andeep arranges his base 10 blocks on the table like this.

Okay, let's count the tens and ones to see how many he has altogether.

So we have eight groups of 10, that's right.

And we can write it in the place value chart like that, can't we? The eight represents eight tens and then we have three more ones.

So we write three in the ones column of the place value chart.

"I know each 10 represents 10 ones," says Andeep.

"I'll use unitizing and counting tens instead of ones," because that's much more efficient, isn't it? So 10, 20, 30, 40, 50, 60, 70, 80.

And now we know that we've counted all the 10.

So now we must count on in ones.

81, 82, 83.

So we have 83 ones.

Laura collects some more base 10 blocks.

She says she has 47 ones altogether.

Is she right? Let's check.

We have seven groups of 10.

So we can write seven to represent the seven tens in the place value chart.

Okay, and then we have four more ones.

So we write four in the ones column at the place value chart, can't we? So we can see there're seven tens and four ones and then we can count them, can't we? So we can count them in tens until we have no more tens and then we count on in ones.

Are you ready? 10, 20, 30, 40, 50, 60, 70, 71, 72, 73, 74.

So we have 74 ones altogether, haven't we? "I must remember to count the tens first then count on in one," said Laura.

So, Andeep places some more base 10 blocks on the table.

There they are.

Look.

"I think there are 39 ones," says Laura.

"I think there are 93 ones," says Andeep.

Who is correct? "We must remember to count the tens first then count on in one," says Laura.

"I will count 10, 20, 30, then count on in one," said Andeep.

I can see now that there are 39 ones.

So what was Laura's mistake? That's right.

She spotted the ones and she counted them first, didn't she? The nine ones, and she counted them as nine tens instead.

Laura drops her base 10 blocks.

I wonder how she should count them.

"I must remember to count the tens first and then count on in ones, she says.

There are five tens.

So that's the same as 50, right? Five tens in the tens column on the place value chart.

And then there are six more ones.

So that will be six in the ones column there, won't there? So there are 56 ones because we count the 50, 10, 20, 30, 40, 50.

And then we count on in ones, 51, 52, 53, 54, 55, 56.

Well done if you did that.

Andeep has tipped out his coins to count them, but Laura thinks they may be tricky to count.

I wonder what you think.

Andeep remembers he can use the tens and ones to help him count them in the most efficient way.

What should he do? I wonder.

"I know I must count the tens first and then count on him ones," he says.

There are six tens, so that's the same as 60, and then there are five more ones.

So we can write your six in the tens column and the five in the ones column, can't we, in the place value chart? So we know we've got six tens, a six p and five more ones.

There are 65 ones.

So well done if you notice that.

Okay, so now it is time to check your understanding again.

The children place some more base 10 blocks on the table.

Which set shows 48 ones? We've got three options there to choose from, A, B, or C.

So pause the video now while you have a think about that.

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

What did you think? Did you notice A? So we can see that it doesn't matter which order the tens and ones are presented in.

We can see that there are four tens and we must count the tens first and then there are eight more ones.

So four tens and eight ones is equal to 48 ones, isn't it? Okay, did you also notice B? So that also has four tens there, hasn't it? And then eight more ones.

So that also would be 48 ones if you counted them in ones.

So if we have a look at C, did you notice that, that did have an eight and a four as digits in the number, but there were actually eight tens, which would be 80, and then four ones.

So that number would have 84 ones, wouldn't it? So well done if you notice that as well.

Excellent work.

Andeep is using the base 10 blocks to measure the length of the shelf.

Oh, let's see how long it is.

He's put in the six of 10 along the shelf and then he counts on in ones, doesn't he? "I used four tens and eight more ones," he says.

I will count the tens in tens and then count on in ones.

So let's help him.

10, 20, 30, 40, 41, 42, 43, 44, 45, 46, 47, 48.

The shelf is 48 cubes long.

Perhaps you could get some cubes in sticks of 10 with some extra ones and measure some things in your room.

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

Laura measures her table using cubes in tens and ones.

How many cubes long is her table? Let's see what she does, and then we have to decide whether it's 43 cubes long, whether it's 34 cubes long, or four cubes long.

Remember to count the tens first, then count on in ones to find out how many cubes long the table is.

So pause the video now while you think about how many cubes long the table is.

Let's see how you did then.

So we can see that's right.

It was 34 cubes long, wasn't it? We can see that she used three tens and four more ones.

So she counted 10, 20, 30, 31, 32, 33, 34.

So it'd be the same as 34 cubes.

The children gather their friends together and play a tens and ones game.

On the count three, they each have to hold up either 10 fingers or one finger.

So there's the fingers that they hold up.

Then they count in tens and ones to see how many fingers are held up altogether.

"We must count the tens first, then count on in ones," Andeep says.

So he's reminding us there, isn't he? So we've got 10, 20, 30, 31, 32, 33.

So there are 33 fingers altogether.

Perhaps you can play this game with your friends.

The children play "I'm thinking of a number".

One describes a number and the other has to guess it.

I'm thinking of a number.

"It has three tens and less than two ones," says Laura.

Oh, I wonder what her number could be.

"Three tens is the same as 30," says Andeep.

Less than two ones must be one one.

It must be 31.

It's the only number it could be, isn't it? Well done if you thought of that as well.

Then it's Andeep's turn.

I'm thinking of a number.

It has less than five tens.

Ooh, so which numbers have less than five tens? "And it has six ones.

What could my number be?" I wonder.

"I know it has six ones," says Laura.

So she knows there's definitely six ones in it.

So she can put out six ones to help her, can't she? Less than five tens means it must have one, two, three, or four tens.

So it could be one 10 and six ones, which would be 16, or it could be two tens and six ones, which would be 26, or three tens and six ones, which would be 36, or four tens and six ones, which would be 46.

So well done if you thought of any of those.

Here's a task for the second part of our lesson.

Each picture shows items that have been stored in tens with some extra ones.

Use each picture to find the missing numbers.

Okay, so you've got these pictures here and then you've also got these pictures.

So pause the video now while you use the pictures to complete the sentences there.

And then here's the second part of our task.

Work with a partner to play "I'm thinking of a number".

Write down a two-digit number, hide it, then give your partners clues so they can guess it.

For example, you might think of 25, write it down and hide it.

And then you could describe how many tens it has, or you could describe how many ones it has.

You could say which numbers it lies in between.

Okay, so pause the video now while you try that.

And let's see how you got on.

So did you do this? So if we have a look at the chocolates, we can see that there are six tens and four ones, aren't there? So we know six tens are 60.

And then if we count on from 60 in ones, we'd go 60, 61, 62, 63, 64.

So there are 64 ones.

Then if we look at the pencils, we can see that there are three tens and five ones, okay? And so we know three tens of 30 and five more will be 30, 31, 32, 33, 34, 35.

Well done.

And then we can see C.

So we've got four tens, haven't we? And then three ones.

So four tens are 40, and then three more is 40, 41, 42, 43.

43 ones.

And then if we look at the money there, we can see there's 10 pennies in each bag.

So four tens and six ones, four tens of 40, aren't they? And then we've got six more ones, 40, 41, 42, 43, 44, 45, 46.

So 46 ones.

And then we've got three tens and eight ones.

So we know three tens of 30 and eight more would be 38 ones.

And then finally, if we look, we have got seven tens and five more ones.

So we will have 75 ones.

So well done if you did that.

You've worked really hard in today's lesson.

You've found out all about how to count larger groups of coins efficiently and how to use our unitizing to help us work out the value, the total value of objects grouped in tens.

So well done.

Okay, so let's look at the second part of our task.

You may have done this.

So here's Laura.

"I'm thinking of a number.

It has two tens and more than eight ones.

What is my number?" And then Andeep says, "Two tens is the same as 20, and then more than eight ones must be nine ones.

So it must be 29." So well done if you did that.

Okay, so you've worked really hard in today's lesson.

Hopefully you're feeling much more confident at counting objects, larger groups of objects when they're grouped in tens, and you can use that to help you count them efficiently, can't you? So well done.

You've worked really hard in today's lesson.

Hopefully you are feeling much more confident about counting larger groups of objects by placing them in groups of 10 and then counting the tens and the extra ones.

So well done.

So let's have a look at what we've learned in today's lesson then.

One item can be used to represent several other items. This is called unitizing.

The order in which tens and ones are arranged does not affect the value of the number.

And we can use a 100 square to help find the value of two-digit numbers more efficiently.

So you've worked really hard today and you've found out lots of new learning that can help you when you are counting your larger groups of objects.

So well done.

I've really enjoyed our lesson today.