Lesson video

Hello, my name is Mr. Clasper, and today we are going to be using direct proportion graphs.

The graph shows the conversion between Canadian dollars and Great British pounds.

Why is this a direct proportion graph? Well, this is a direct proportion graph, because it's a straight line moving from the origin.

There is a multiplicative relationship between the British pounds and the Canadian dollars.

Let's use the graph to convert £40 to Canadian dollars.

We need to find £40, and follow this up to the graph.

Then, if we read off, they should give us 68 Canadian dollars.

So £40 is equivalent to 68 Canadian dollars.

Let's convert 40 Canadian dollars to pounds.

So we're going to read off from $40, and then read down.

This will give us £23.

So this means that 40 Canadian dollars, is equivalent to £23.

Here is a question for you to try.

Pause the video to complete your task, and click resume once you're finished.

And here are your solutions.

So remember just read from the graph carefully.

So 60 pints into litres, if you read from 60 pints on the graph on the X-axis and read up to the graph, you should find that the response should be 34 litres.

And if we repeat this process for parts B and C, but you're going to read from the Y-axis, or the litres axis, and read across your graph, you should find the correct answers.

Here is another question for you to try.

Pause the video to complete your task, and click resume once you're finished.

And here are your solutions.

So plotting the graph is similar to plotting a scatter graph.

So if you plot 10, 11, and then 20, 22, and 40, 44, et cetera, and join this with a straight line from the origin, you will create your direct proportion graph.

And for part B, to explain how you know the currencies are in direct proportion, the graph is a straight line, therefore, it must be in direct proportion.

Here's your last question.

Pause the video to complete your task, and click resume once you're finished.

And here are the solutions.

So remember a direct proportion graph must start from the origin, and it must be a straight line.

Therefore, the only two correct graphs would be C and D.

And that is the end of our lesson on direct proportion graphs.

Why not give the exit quiz a go? I'll hopefully see you soon.