A short KS2/SATs-focused YouTube lesson (presenter Clare) teaching how to use bar models to find the whole from one or more parts. The video walks through an example: oak class has 18 boys and 1/3 of the class are girls; Clare draws a bar split into thirds (reminding students to draw one fewer dividing lines than the fraction) to show 2/3 = 18, hence 1/3 = 9 and total = 27. The clip emphasizes checking the question and common student errors when dividing models.
Chapters
Hello, my name is Clare and we're going to look at bar models and how we can use them to find the value of the whole when we've been given one or more parts. So let's start by having a look at the question. And this is a typical question that you will find at Key Stage 2, SATS. So this is a great way to help your year six children because only about 15% of children can actually do this. It's because they read the question and they get confused. If you can draw a bar model, it makes it so much easier. Ok, let's have a look. It says in oak class there are 18 boys, 1/3 of the class are girls. How many children are there in oak class altogether? Okay, it sounds confusing when you first look at it, but let's start by drawing a bar model to represent oak class. Here we go. Alright, I'm going to label that oak class, nice and easy to start with. Then I look again at the question. I always teach children to go back and look at the question. Keep checking you've got all the information that you need. Okay, I'm having another Look. There are 18 boys. All right. And next thing tells me one third of the class are girls. So I'm going to put a third of the class onto my bar model. Now, another thing you need to say to children is because they often get this wrong, when they're going to draw lines to turn something into thirds, they think they're going to draw three lines. Always say to them, when you're dividing a bar model up, you need to remember this is the main teaching point here. You draw one line less than the fraction that you're doing. So if I'm dividing my bar model up into thirds, I'm going to do two lines. If I was dividing it up into eights, I do seven lines. In this case, we're going to do it into thirds. So I'm going to draw two lines, also going to try and make it look that they are roughly equal to represent thirds. Alright. And I know that one third of this class, my bar, is girls. So I'm going to put my girls in. Here they are. Okay. The next thing I'm going to look at is the fact I've got one third. I could then ask the children, so who is going to make up the rest of the class? Who have we? Obviously we know there are boys, so I'm going to put them onto my bar model as well. So I've got boys here and boys here representing the whole class. Now I'm hoping that this point, the children will have worked out that actually if you ask them what fraction of the class of boys they should be able, just by looking at the bar at this point, be able to say to you, two thirds of that class are boys. Okay, because of the way you've drawn it. And if I look back at the question, it tells. I can also ask the children to tell me again, how many boys is that altogether? And they should remember that. So 2/3 of the class here represent 18 boys. Okay, so if I've got 2/3 of the class represent 18 boys, okay, I can then say to the children, how many are there then in one third? Now, because I've drawn it like that, I would hope that because I've got 18 boys here, they can see 2/3. I actually need to halve that number, 18 to find 1/3. So I'll have nine boys in 1/3. So I'm going to put that onto my bar model. So I've got nine boys here and I've got nine boys there. I then ask the children, right, how many girls have I got? If one third is nine boys, I've got another third here is nine boys. I've got one third girls. Hopefully they would know that's going to be nine girls as well. Now, the problem is a lot of children stop at this point, they think they've done it. Okay, it's a teaching point here to say, right, let's go back and read the question again. Let's check, have we worked everything out? Do we know the answer to this question? Okay, so if I look again at the question at the end, it says, how many children are in oak class altogether? And we haven't done that yet. Okay, so I'm going to look back at the bar model now. Some children will look at it straight away and see they've got three nines, a 27. So they'll go, three nines are 27 children. Another way they could solve this problem is by looking at the fact they've got 9 add 18. They could work it out by going, 9 add 18 gives them 27, and now they are sure that they've answered the question. So that's how we use a bar model to find the value of the whole. When you're given one or more parts.
