Lesson video

Hi, I'm Mrs. Dennett.

In this lesson, we're going to be looking at ratios, specifically finding the total or difference given a part.

In this question, Tom and Mo are sharing some money in the ratio of five to one.

We can represent this in a bar model.

So Tom gets five parts or five boxes, and Mo gets one.

All of the boxes have to be equal in size.

We know that Tom gets 80 pounds, so we can represent that with a little bracket above Tom's boxes and 80 pounds.

We want to know how much more does Tom get than Mo? So here we are looking for a difference in the amount that Tom gets compared to Mo, and that can be found here.

So we know that Tom gets 80 pounds, we can share this equally between Tom's boxes.

So we can see that Tom gets 16 pounds in each of his boxes.

And likewise, because all of the boxes are equal in size, Mo also gets 16 pounds in his box.

Now there are a couple of ways that we can work out the difference.

We know now that Tom has got 80 pounds and we can see that Mo has got 16 pounds.

So we could just do 80, take away 16, which is 64 pounds.

Another way that we could work out how much more Tom gets than Mo is to look at the number of boxes that Tom has got.

Well, he's got four more boxes than Mo.

So there's a difference of four boxes between Tom and Mo.

So we could do four times 16 because there's 16 pounds in each box.

And again, that gives us 64 pounds.

So Tom get 64 pounds more than Mo.

In this question, Emma is making some juice.

We start by drawing a bar model.

So we know from the ratio that we've got two boxes for cordial and seven boxes for water.

We're also told that Emma has got 357 millilitres of water.

So we can put that label on our diagram as well.

We want to know how much juice she's making in total.

So that's the total of all cordial used and all the water used.

Okay, so let's start with the fact that we've got 357 millilitres of water, and this is shared between seven boxes.

So we get 51 millilitres in each box.

Notice we've also got 51 millilitres in our two boxes for cordial because all of the boxes are equal in size.

Now there are a couple of ways that we can now find the total amount of juice that Emma is making.

So we can see that we've got two boxes for cordial both containing 51 millilitres.

So this would be 102 millilitres of cordial.

We can then add together the amount of cordial and the amount of water that we've got.

So you can see I've done 357 add 102, which gives us 459 millilitres of cordial and water, so 459 millilitres of juice all together.

An alternative method is to notice that we've got nine boxes altogether.

So these nine boxes have all got 51 millilitres in them.

So we can do nine times 51, which gives us 459 millimetres.

So we've got the same answer, but there're just a couple of different ways of getting it.

And you can choose which method you prefer.

Or you could even use both to check your answers.

So we can see that Emma is making 459 millilitres of juice altogether.

Here's a question for you to try.

Pause the video to complete the task and restart when you have finished.

Here are the answers.

For part A, once you have worked out that there are five stickers in each part, we can see that Gracie gets 15 and Mo has 20.

And this is a difference of five.

For part B, we add together Gracie's 15 stickers and Mo's 20 stickers to get 35 stickers altogether.

For part C, Mo gives Gracie 10 stickers, so she now has 25 stickers and Mo will have 10.

25 to 10 simplifies to five to two.

Here's a question for you to try.

Pause the video to complete the task and restart when you have finished.

Here are the answers.

We're given that the length AB is nine centimetres, divide this into two parts to find that each part is worth 4.

5 centimetres.

Then find the length BC.

4.

5 times seven is 31.

5 centimetres.

Find the difference between 31.

5 and nine to get 22.

5 centimetres as the difference.

For part B, we add five centimetres to 31.

5 to get the length AC.

This will be 36.

5 centimetres.

Add all of the sidelines together.

So that's 36.

5 add 31.

5 add nine to get perimeter of 77 centimetres.

Here's a question for you to try.

Pause the video to complete the task and restart when you have finished.

Here are the answers.

For part A, we find the total of all the parts, 30 apples and 55 bananas is 85 pieces of fruit.

For part B, John eats 10 apples so there would be 20 apples left.

The new ratio will be 20 to 55, which simplifies to 4 to 11 when you divide by the highest common factor of five.

Here's a final question for you to try.

Pause the video to complete the task and restart when you have finished.

Here are the answers.

using the fact that there are 24 hours in a day and the information that's given in this question, we can draw two bar models.

One for Monday and one, separate one for Saturday.

You'll find that Mike sleeps for eight hours on a Monday and 10 hours on a Saturday.

This gives us a difference of two hours.

That's all for this lesson.

Remember to take the exit quiz before you leave.

Thank you for watching.