A short YouTube lesson (presenter: Ellie) demonstrating how to use a comparison bar model to solve a multi-step fraction problem. The problem: Ollie and Beth start with the same amount; Beth spends 2/3 and has £1.64 change, implying a starting total of £4.92. By partitioning the bars into twelfths the presenter finds one twelfth is £0.41 and calculates Ollie’s spend (10/12) as £4.10. The clip is a single-speaker instructional walkthrough focused on model drawing and arithmetic steps.
Questions this video answers
Ellie
£1.64
£4.92
£0.41 (41p)
£4.10
Chapters
Hi, I'm Ellie, and in this video, we're going to be looking at how to solve a more challenging fraction problem. And to solve this, we're going to be using a bar model, but we're going to be using a comparison bar model. So let's have a look at the question and then see how we can use our bar models to help us. So Ollie and Beth have the same amount of money to spend. Ollie spends 10 twelfths of his money on a toy car And Beth spends 2/2 of hers on a pencil case. She gets £1 64 change. And the question is asking us to find how much did Ollie spend? Now, to solve this question, to begin with, we want the pupils to spot that Ollie and Beth have the same amount of money. And that is why I've drawn two bars. One for Ollie, one for Beth. They're exactly the same. The next thing we want to do is find out what information we know. So we know that Beth got £1.64change after spending 2/3. So at this point, you'd want to say to your pupils, how can we represent that on Beth's bar? Now, what they want to do is split it into three equal parts to represent the three thirds. So if we divide that bar up into thirds, which part did she spend? She spent these two parts. So this part is her change. And we know from the question that this is £1 64. The next question that you would want to ask your pupils is, if I know that that's one third, that's her change, how can I find out the whole amount that she had to begin with? And hopefully they should see easily from the bar model. They just need to multiply 1 pound 64 by 3. So they can do that. They might use a formal written method or mental methods to find the answer, and that would give them a total of £4.92. So this bar here, the whole thing is £4.92. So what does that tell us? You can then ask them about Ollie's bar. That means overall his he had £4 92. But what is the question asking us? It's not asking us how much Ollie had to begin with, it's asking him how much he spent. So you then need to go back to the question and say, what do we know about Ollie? Let's have a look. So we know he spent 10, 12 of his money. So now we're going to represent this on this bar. Now, I can use my thirds to help me here to split this into 12 equal parts. So here I've got three. If I split each of these into four parts, that will help me represent these twelfths to the pupils. Obviously, you'd want to get them to do it quite precisely so that you can show that those twelfths are equal parts of the bar. So Ollie spent 10 twelfths. So the thing I want to work out is 10 lots of each of these. Okay, So I want to do the £4,92, which is the whole thing, divided by 12, to find out how much each of these is. Again, pupils can use a written method to do that or a mental method that they feel comfortable with. So they should get the answer then that each one of those small bits is 41p. So then you need to ask them, how do we find out how much you spent altogether? If it's 10/12, they simply need to multiply the 41p by 10. So timesing that by 10 would give them 4 pounds and 10p. So overall, we can say that Ollie spent 4 pounds and 10p, and that's how you can use the bar models to help you solve more challenging fraction problems.
