Lesson video

Hi, my name is Miss Woodall, and I'm really looking forward to taking you through this lesson.

For this lesson, you'll need a pencil and paper.

If you need to pause the video now to go and get these items, please do that.

To start with let's have a look at the practise activity Mr.Blake had left you with from the previous lesson.

Can you draw a number line to represent this equation? 75 subtract 50 equals 25.

I had a good drawing the number lines represent this equation.

Did your number line look similar to mine? We would then ask to think of a context that uses this calculation.

Mr. White had suggested that we use measure or money, mass, length, temperature, or time.

And we have to think about some questions we could ask about this context where you'd need to find out the difference.

Here are two of the ones that I thought of.

My brother has 75 pounds in his savings and I have 50 pounds, how much more does he have the than me? Here we would have to find out the difference between 75 and 50, which is 25.

My second example was my grandma is 75 years old and my mom is 50 years old.

What is the difference in their ages? Again, to find the difference we could do 75 subtract 50 to get 25.

Let's move on to our learning for this lesson.

We are going to continue to look at difference.

Here we have a graph showing the difference in age between Max and his dad Jim.

When max was born, Jim was 25 years old.

Therefore, what is the difference between their ages? Yes, that's right 25 years.

You can see that here marked by their [indistinct].

When Jim is 30, Max is only five.

So what's the difference between their ages now.

Yes, that's right it's 25 years.

When Jim is 35, Max is only 10.

The difference in their ages hasn't changed it is still 25 years.

When Jimmy's 40, Max is 15.

What is the difference in their ages now? Yes, that's right 25 years.

When Jim is 45, Max is 20.

The difference in their ages hasn't changed it is still 25 years.

Is the difference between their ages always going to remain the same? Yes it is.

So can you tell me how old will Max be when Jim is 75? Pause the video if you like and have a go at working it out.

Well done when Jim is 75, Max will be 50.

What do you notice each time when we change Jim's age, what happened to Max's age? That's right, did you say when Jim's age changed, Max's aged changed by the same amount? This meant the difference always stays the same well done.

Now let's have a look at another context.

Here is Jack and he has a three-liter bottle of water and Sila has a two-liter bottle of water.

They both pour out three, 250 millilitre glasses of water.

What is the difference between the amounts in their bottles after each glass is poured? Let's have a look at how we could display this.

To start with I need to think about how many millilitres is in one litre? Yes, that's right 1000 millilitres.

So how many millilitres is in Jack's bottle at the start? 3000 millilitres and how many are in Sila's bottle? That's right 2000 millilitres.

What's the difference in their full bottles? Yes 1000 millilitres.

I can work this out by doing 3000 millilitres subtract 2000 millilitres to give me a 1000 millilitres.

Now, if they've both poured one glass of 250 millilitres out, Jack would now have yes, 2,750 millilitres and Sila would have 1,750 millilitres.

What's the difference in their amounts that they now have in their bottles? Yes, still a 1000 millilitres.

I can work that out by doing 2,750 millilitres subtract 1,750 millilitres to give me a 1000 millilitres.

What about if they pour another glass of 250 millilitres.

Jack would now have 2,500 millilitres and Sila would have 1,500 millilitres.

But what's the difference in their amount that they now have in their bottles? Yes, it's still a 1000 millilitres.

I can work this out by doing 2,500 millilitres subtract 1,500 millilitres to give me a 1000 millilitres.

Finally, they're going to pour out another 250 millilitres each.

I'd like you to now pause the video and see if you can calculate what the next values would be in the table.

And what's the difference in their bottles now? Pause now.

Well done, did you get the same as me? Jack would now have 2,250 millilitres and Sila would have 1,250 millilitres.

What about the difference, did you calculate it like me? 2,250 millilitres subtract 1,250 millilitres to leave a 1000 millilitres, if you did well done.

Let's look at both of the graphs now that we've just studied.

What did you notice about both of them? What's different in each graph? Did you spot that one was vertical, here it is.

And one was horizontal, well done if you did.

What's the same about both graphs? That's right the difference every time.

In the first one, Jim and Max's ages had a difference of 25 years every single time.

And in the second one, Jack and Sila's bottle had a difference of a 1000 every single time.

So the difference is staying the same when we change the other values by the same amount each time.

Now it's over to you and your towns have a practise.

Here we have a bus timetable the journey time from school to the bus station is 15 minutes long.

So you can see the first one as an example.

If we leave school at 8:00 am, we will arrive at the bus station at 8:15.

So therefore it's taken us 15 minutes.

I'm going to leave you to have a go at filling in the rest of the bus timetable.

And if you're ready for a challenge, why not try this last one? Can you think of your own times with a difference of 15 minutes? Thank you for joining me for this lesson and I hope to see you again very soon.