Hi year 2 students. Welcome back to numeracy lessons with your teacher Ella. We are up to
lesson eight. Now let's have a think about what our last lesson was quickly. Part - part - whole
with our cherry diagrams. Remember, they looked like cherries and we had a look at a whole number,
and we put them into different parts. Part - part, maybe another part, makes our whole and we played
a fun game called the Part - part -whole card game. I hope you had fun with that. You might
still be playing. It's a great way of learning how to partition numbers into smaller parts, breaking
them into little parts to make it easier for you to use and be real flexible with your numbers.
All right, so where are we now? Today's lesson is about our bar models, but, before we get there,
let's get to our warm up. All right, let's focus on here now (Presenter points to display board).
How many dots can you see? It's a bit trickier than the last time we did it.
How many parts? What is it as a whole and can you write a sentence, a number sentence,
that shows us what we can see here? (thinking time)
How did you go? Let's have a look. How many dots can you see? I wonder if you saw it this way.
I can see that these are 10 frames and I can see that there are
four of those. One, two, three, four. If I can see four there and I can see two over here.
Okay, or maybe you saw a little bit differently. Maybe you saw a two, a two and a two.
Let's write those down. So, I saw a 4 lots of 10, remember. How am I going to write that?
Four lots of 10. Four lots of 10 is 40. I can see 40 and I can see a two lots of 10. Two lots of 10
make 20. So I can see these dots make one part, these dots make the other
part. Part - part - part - part and we'll get to the whole. Let's have a look at the other
way I saw it, remembering you might have seen it a different way too. So I saw a two lots of ten.
I saw a two lots of ten and I saw a two lots of ten. Okay let's get to it.
Let's try here first. Twenty, plus twenty, plus twenty. Hmm,
two plus two, plus two. Maybe? Let's have a think about this.
20 plus 20 plus 20 will make our 60. I'll just check. Two, two and two will make 6. Good
and let's have a look at 40 plus 20. Let's think about the 4 and the 2. The 4 and the 2 will give
me 6. So, this must be 60. Both of these are correct. I wonder if you saw it in that way.
Let's get to our bar models. What on earth do they look like? Well today our learning intention is to
represent these parts by making whole - part - part - whole on our bar models. All right, we'll
know we can do this when we use the bar models to find all the numbers in a whole number. All right,
what does that look like? Well I've got two bar models here. So before we draw our own,
let's have a look at these ones. This is what they look like and I'm going to start with the number
15. What does 15 look like? Well here it is. I have made a group of 15. This is our
whole number and it sits nicely in our bar model. Now let's not get worried
about our bar model being exactly correct. Doesn't have to be the exactly correct size.
All right, so that's number one. Here's our 15. How can I make 15 in two parts?
Well I'm going to show you two different ways to do that. The first way I want to show you is,
a 10. Fifteen whole is a part 10 and a part 5. So I can see that 15 is a 10 and a 5.
I can also see that a 15 might be, let's have a look and see how many I've got
here. (counting) Two, four, six, eight. It might be an eight and two, four, six plus one seven.
So what have we ended up with? We've ended up with this beautiful bar model which shows us
a whole and it's parts. All right, so this is how we write our bar models. Let's give it a go.
Okay, let's try some of these bar models, remembering that we're going to try and
stick to our groups of 10, because we know that that's a really efficient way of counting and
grouping. Here we go. So, when I draw a bar model I start with a rectangle and I cut it in half.
Now remember, the sizing down here (points to bottom row) doesn't really matter, but when I
know I've got a big number, I'll probably give it a bit more space than the smaller number. So, I'm
going to think of a number that I really like. 27. Okay, now I need to cut it up into groups of ten.
So, I'm going to have a look at my tens here and think, okay this is going to be the larger part.
Let's make this a 20 and a 7. Here's my bar model of 27 is made up of parts 20 and 7. What a great
bar model to start with. All right now let's add that number sentence. 20 plus 7 equals 27.
Let's try another one. I'm going to go a bit bigger this time. So here is my bar diagram
and I'm going to cut it in half again. At the top I'm going to place my whole and this time
my whole is 85. Just pluck that number out. So here we go. 85 how many tens? Oh, I have eight
tens and I know this is a bigger thing, so, I'm just going to make that space
a little bit bigger. So here we go. Eight tens is 80 and my five ones. 85 is a whole
and here are my parts. 80 and 5. Let's turn it into a number sentence. 80 plus 5 equals 85.
Okay, I think we're ready. Let's go past 100. Here is my bar diagram. Remember it's a rectangle
and I'm going to cut it in half. Let's think of a big number past 100. Let's go for 213.
What a great number, 213. How am I going to partition this whole? How many parts?
Well I can see now I have a 200. It's in the hundreds. 200. This is the bigger one,
so I'll make it a little bit bigger (presenter demonstrates). Here is my 200.
Let's look at my tens. Let's pull it apart. Here is my ten. One ten
and here is my ones. How many do I have in my ones? I have three. So,
my bar model is showing me 213 is made up of three different parts, and those parts are 200
and 10 and 3. Let's write that down. 200 and 10 and 3 will give me 213.
And there we have it my friends, three beautiful bar models for us to learn from!
What's next? It's your turn. So, let's have a look at some of them for you to do by yourself.
Here are some bar models with the whole numbers 12, 75 , 426 and here's (presenter points to last
bar diagram) choose your own number. That's kind of fun. All right, don't forget this is how we
partition numbers using bar models. We have the whole and the parts underneath. All right,
press pause and add these to your learning book. (Time to do bar models.)
Okay, let's reflect on our lesson today. Remember we used bar models to help us structure our
thinking of part - part - whole. It helps us to partition in hundreds, tens and ones. All right,
here are some stories today for you to do in your books. They start with - there were 24 marbles in
a bag, 20 were red and 4 were blue. You'll need to draw a bar model to represent that story.
Second one. 100 people were watching a basketball game.
50 of them were cheering for the blue team and 50 were cheering for the red team. I wonder who won?
The last one is - there were 50 balloons. There were 30 pink balloons and 20 green balloons. How
will we structure our thinking in a bar model? You might like to make your own here as well.
Okay, all the best and I'll see you at our next lesson. Happy mathematical thinking!