A short instructional video (presenters Ellie and a co-presenter) demonstrating how to develop greater depth understanding in ratio and proportion using a bar model. The example: cars to motorbikes are in ratio 9:2, with 56 more cars than motorbikes; the presenters show that the 56 corresponds to 7 equal parts (56/7 = 8) and that the total number of vehicles is 11 parts × 8 = 88. The lesson emphasizes identifying equal parts from relational information and multiplying to find totals.
Questions this video answers
9 to 2
56
7 equal parts
8
88
Chapters
Hi, I'm Ellie and in this video.
We'Re going to look at how you.
Can get your pupils working at greater.
Depth when they're looking at questions about ratio and proportion.
So pupils who are working at greater.
Depth in this area should be able.
To identify the value of equal parts in a question when they're only given the relationship between those parts.
So here's an example of that type of question.
The ratio of the number of cars to the number of motorbikes in a car park is 9 to 2.
There are 56 more cars than motorbikes. How many vehicles are there altogether?
So, first of all, as with any.
Question, you'd want to ask your pupils what information we have.
So we know the ratio is 9.
To 2 and there are 56 more cars than motorbikes.
So a bar model is a really.
Nice way to represent this problem. So we're going to start with representing the motorbikes. So M is for my motorbikes and I'm going to put the cars underneath it.
So I know that the ratio of.
Motorbikes to cars is nine to two. So for each of my two equal parts for the motorbikes, I have nine of those to represent the number of cars. So three, four. And it's really important to have these as equal sized parts because it represents to the pupils that that is part of the ratio. 7, 1, 2, 3, 4. 1, 2, 3, 4, 5, 6, 7, 8, 9.
Okay, so we've got nine equal parts.
Here and two here. Now, the other bit of information we know is that there are 56 more.
Cars and you can get your pupils.
To label this here 56 more, and.
Then they should be able to see.
That this 56 is represented by these 7 equal parts here. And to work that out how much each of those equal parts is, then they're just going to do 56 divided by seven, which gives them eight.
So you need to make sure they've.
Understood that that 8 represents each equal.
Parts and they can label that if they want to on each section to.
Show that each one of them is 8. Go back to the question. What is it asking you? It's not asking you how many equal.
Parts this is or how much is.
In each equal part.
It says how many are there in.
The car park altogether? So if each part is worth eight.
You need to know how many equal parts you've got.
You've got nine here and two here.
So you've got a total of 11 equal parts.
So to find your answer, you just.
Do 11 times by eight, which is 88.
And that's how pupils can use the bar model to help solve more complex ratio problems.
