Lesson video

Hello guys, welcome to our next lesson, where we are going to be drawing bar models to help us with measuring word problems, okay.

So we're going to be looking at everything we'll learn about bar models and we're going to bring it all together for this lesson.

Let's go.

Okay we're going to start with calculations with mixed units and we're going to do slightly different questions that we've not done before.

We're then going to be reviewing bar models, and that's going to be in all calculations now of what we've done.

That's addition, subtraction, division, and multiplication.

Bar models with measure on word problems, which will get you guys ready for your independent task, and then you're going to come back to me to do your answers.

So you are going to need a pencil and a ruler to draw your wonderful bar models.

A rubber for any mistakes that you might do.

okay.

And an exercise book to put in all your great work.

Okay so we're going to start with calculation mixed units.

I know we've done this before and we feel very confident when doing them, but I'm going to just show you what happens when it goes more than 1000 millilitres.

Just like in this question.

So we have 900 millilitres plus 400 millilitres.

That gives us 1300 millilitres.

Now we need to leave our answer in mix units.

That means in litres and millilitres.

So how do we do that? Well, I'm going to split up my 1,300 millilitres into 1000 millilitres plus 300 millilitres, okay.

And I am going to do that because I know that 1000 millilitres is equal to one litre.

Therefore I can write 1300 millilitres as one litre and 300 millilitres, okay.

So have a moment and just have a look at what I just did there.

And this is this process that you're going to do whenever you come across this question.

Okay, I want you to help me do the next one.

So we have 400 grammes times by three.

Now, if I know four times three is equal to 12, then I know 400 grammes times three is equal to 1,200 grammes.

All right.

So now what I'm going to do is I'm going to take that 1,200 grammes and I'm going to leave it in mixed units.

That means in kilogrammes and grammes, how do I do that? Well, I know that I can write 1,200 grammes as 1000 grammes plus 200 grammes, okay.

The reason why I'm doing that is because I know that 1000 grammes is equal to one kilogramme.

Good.

Therefore I can write 1200 grammes as one kilogramme and 200 grammes.

Well done guys, okay.

I think we're ready to try it for ourselves.

Here we go.

So we have three litres and 400 millilitres multiplied by three.

Pause the video, and I'd like to answer this question for me.

Off you go.

Okay guys, you're back.

So let's find out the answer.

The answer is, it was 10 litres and 200 millilitres.

Okay let's find out how we got to the answer.

Right so three litres and 400 millilitres multiplied by three.

What's the first step that we do? We group our like terms. Really good, okay.

So we need to group our litres and our millilitres.

Then what's the second thing? We need to multiply each unit separately.

really good.

So that's three litres times by three and 400 millilitres times by three, which is equal to 1200 millilitres.

And here we go.

This is where we're going to practise what we just learned.

Okay, so what do we do? 1200 millilitres is equal to 1000 millilitres plus 200 millilitres, right.

And I know that 1000 millilitres is equal to one litre.

So I can write 1200 millilitres as one litre and 200 millilitres.

Okay so thinking about that then when I come to my answer, I know that I need to do nine litres plus one litres and 200 millilitres, which gives me 10 litres and 200 millilitres.

So have a moment to have a look at what we just did.

Now the operation has become a little bit longer, okay.

But you've given you answers in mixed units.

And that's what we're looking for, in litres and in millilitres or in kilogrammes and in grammes.

Right so we're going to start reviewing some bar models together okay.

So I'm going to show you some different bar models of different types of operations.

So that's addition, subtraction, multiplication or division.

And we're going to talk about what we know, what we don't know and how we get to our answer for that calculation, okay.

Right, so having a look at this bar model, the first thing I know is we know the two parts.

We know the value of the two parts.

We know that two parts make a whole and we know that's why they're just in one bar, okay.

The whole is unknown.

That's really important for us to know.

And you need to add the two parts to make the whole.

That's what we need to know as well.

So remember part whole.

So in order find the whole, we need to add the two parts together.

Your calculation is going to be 256 plus 178.

All right guys.

Really good Remember always asking ourselves what do we know, okay.

Right, next one.

Reviewing our bar models.

Can you help me with this one then please? So what do we know? We know the whole is 134.

Okay, that's good.

We know that one part is 96, okay.

We know there are two parts in one whole.

Okay, that's really important.

We do not know one of those parts.

So it'd be this one right here.

And how do we get there? Well, you need to subtract the known part from the whole to get the unknown part.

So the calculation should be 134, take away 96, which is equal to 40.

Right, Your turn guys.

I want you to pause the video and I want you to try this one for me, and then come back when you're done.

Off you go.

Right, you're back.

Here we go.

You ready for the answers? I'm sure you guys are great by this by now.

And if you're not, don't worry.

Keep practising , you'll get there.

Ready and, option number three.

Okay, So let's have a look.

The whole is 125.

Absolutely it is.

There are two parts that make the whole, good.

That's one, two parts that make this whole, okay.

The value of one part is 78, okay.

And we know that the calculation has to be, well if we trying to find one part, that means we have to subtract one of the parts from the whole, which is 125, take away 78.

Well done guys.

Really good work.

Okay.

Now we're going to review bar models with multiplication and division.

So we have this one right here.

What do we know and what do we not know? Okay, well the value of one part is 10.

That's something I know.

We know that the value of the other parts are known, okay.

But it is three times less than the whole.

Remember we said three times less, we're dividing.

okay.

What is unknown? The whole is unknown, okay.

So in order for us to get the whole, what do we need to do? Well, we need to multiply the value of the one part by three to find a whole.

The reason why we're multiplying by three is because it is the inverse of dividing by three.

The inverse of dividing by three is multiplying by three.

Therefore our calculation will be three times 10, which is equal to 30.

Okay, so this is another one and this time I need your help okay.

So what do we know? let's have a look.

This is the whole, right? No, you're right.

Sorry, that is the part okay.

And this is nine times less right? No, you're right.

Sorry, it will be nine times bigger okay.

Nine times less would be showing me a division there.

Okay so the value of one part is three.

It's good to know.

The value of the other parts are unknown, but it is nine times bigger than three.

What is unknown? Is it the parts? Nope, it is the whole, so the whole is unknown.

So how do I get my value of the whole, what do I need to do? Well, I need to multiply the value of my one part, which is three by nine to find the whole, okay.

And that would give me three times nine, which is equal to 27.

Right, I think you guys are ready to try it for yourselves.

Here's a question for you.

I'd like you to pause the video and then come back when you're done.

All right guys we're back.

Are we ready to find out the answer? Option number two.

Let's find that.

Let's check out if this is correct.

Okay so the whole is unknown.

Yup, hat is correct.

The value of one part is seven, good.

The whole is four times less, good.

Four times less than the value of the parts.

And in order to find the whole, you need to multiply.

Okay, because it says divide here.

So we do an inverse by one part, okay.

So there we go.

Four times seven.

And that is our answer.

Well done guys.

Good work.

All right, let's go to the next part.

Okay so now we're going to be drawing bar models to represent word problems again.

And this is an all our calculations of addition, subtraction, multiplication, and division.

So let's start by reading our question first.

So Addy had a sunflower that was 340 centimetres tall.

Overnight the strong wind snapped the sunflower and broke off 185 centimetres.

How tall is Addy's sunflower now? Well, we know that the whole is 345 centimetres.

Okay.

And we know that what broke off.

So something that came off of our whole okay, was 185 centimetres.

And what do we not know? Well, we don't know the value of the sunflower now okay.

After it's been snapped off that poor sunflower.

So, because I can't.

Too many sunflowers have been lost during this process.

Okay, sorry.

Right, so our bar model should look like this.

Really good guys.

Now using this we're now going to figure out what the calculation is.

So as I said, if we don't know our parts, that means that we do whole, takeaway part to find a part.

Okay.

In that case our calculation is 345 centimetres take away 185 centimetres, which is equal to 160 centimetres.

Right, it's time for you guys to have a go.

So Pierre completed level 12 in his game, but had 112 points taken away for not finding all the treasure.

That's a bit mean.

His final school was 276.

How many would he have scored if you'd found all the treasure? So you're going to pause the video and I'd like to match the bar model to the word problem.

off you go.

Okay, back with me.

Are we ready for the answer? The answer is option number three.

Let's check though okay.

So let's find out.

So we know that in this game he had 112 points taken away.

Okay so that's one of our parts and his final score was 276, but that's after they took away his points right.

And we're trying to find out how many would he have scored if he'd found all the treasure? So that would be our whole.

So in that case, the whole is unknown.

Just like it is here, okay.

This is the part that was taken away.

And this is how much he was left with.

So this is why this is the correct answer.

Well done guys, great work.

Here we go to the next one.

So Addy had three boxes of chocolate fingers.

Each box of chocolate fingers weigh two kilogrammes and 300 grammes.

What was the weight of all three boxes? Okay, so what do we know? Well I know that there are three boxes.

So that means that there's three equal parts.

So that's going to go there.

I know that each part is equal to two kilogrammes of 300 grammes, but what we don't know is, is our whole.

Okay.

So then our bar model should look like this.

So what is the calculation? Now remember when it comes to multiplication and division, if we don't know our whole, then we need to multiply the number of equal parts by the value of one part, which would give us two kilogrammes and 300 grammes times by three.

We separate our units, okay.

To get two kilogrammes times by three and 300 grammes times by three.

And then we left with six kilogrammes and 900 grammes.

Okay, that's your answer.

I think it's ready for you guys to have a go.

So Mr Slade used 900 centimetres of string to tie up the bags of rubbish he had collected, There were three bags that needed tying up.

How much string did Mr Slade use for each rubbish bag? I'd like you to pause the video, and match the bar model to the word problem.

Off you go.

Okay, back to me.

So which one is it going to be, ready and, option number two.

Well let's double check this okay.

So we know that he used 900 centimetres of string to tie up all the bags.

Well then that would be our whole.

If there were three bags, that would be the number of equal parts.

One, two, three.

And we're trying to find out how much string he used in each rubbish bag, which is why one of our parts is unknown.

Well done guys.

Really good work.

It is time for your independent task.

Right, you've got four word problems to go through today.

And there are a mixture of addition, subtraction, division, and multiplication.

Follow all the steps.

Always, what do I know, what do I not know, what do I need to do and then the calculation.

Good luck.

I'd like you to pause the video now.

You're going to to go to worksheets and you're going to come back here where I'll be waiting for you to go through the answers.

Okay, welcome back.

So let's read our question first.

Mr Nieto was trying to water everyone's sunflowers.

See, I just really care about them.

It's just we've lost so many.

He used a measuring bucket to get 12 litres and 200 millilitres from the hose.

A hole in the bottom meant that two litres and 150 millilitres leaked away.

How much water did he have left for the sunflowers? So this is our bar model.

And what do we know then? We know that our hole is 12 litres and 200 millilitres.

Okay, cause that was the, how much was in the one bucket.

We also know that there's two parts within that hole.

That's why one of the parts in there that leaked away was two litres and 150 millilitres.

And what do we not know? There'll be one of our parts, okay.

So what calculations can we get out of this? Remember if we're trying to find out the value of one of the parts, it will be whole takeaway parts.

So in this case, it's 12 litres and 200 millilitres take away two litres and 150 millilitres.

So we are going to group our like terms first and we're going to subtract them, okay.

Which leaves us with 10 litres and 50 millilitres.

And then we bring them together for a answer of 10 litres and 50 millilitres left in the buckets.

Well done guys.

if it doesn't look like mine, fix it now.

Let's go to the next question.

Right, Pierre and Alex collected cans for recycling, weighing them each month.

In June they collected two kilogrammes and 800 grammes and in July they collected another one kilogramme and 400 grammes.

What was the weight of the cans they collected altogether.

Okay, so your bar model should've looked like this.

Okay.

Where one of your parts was two kilogrammes and 800 grammes.

And the other part was one kilogramme and 400 grammes.

And a whole is unknown, okay.

But we're trying to figure out what it is altogether.

So what's the calculation? Remember when we don't know the whole, we need to add our two parts together, which would give us this calculation right here.

Okay.

Then we need to group like terms, which leaves us with two kilogrammes plus one kilogramme, is equal to three kilogrammes and 800 grammes plus 400 grammes equal to 1200 grammes.

And this is where we go back to what we did at the start.

So 1200 grammes, how can we write that in mix units? So I know that 1,200 grammes is equal to 1000 grammes, which is one kilogramme plus 200 grammes.

So I can write it like this, as one kilogramme and 200 grammes.

Now we need to bring it all together, which will leave me with three kilogrammes plus one kilogramme and 200 grammes.

And I'm again, grouping my like terms again, which leaves me with four kilogrammes and 200 grammes.

Okay, let's go on to the next one.

Let's read it first.

Judy, Hannah and Aliyah collected rain water for the sunflowers each week.

In the first week they collected three litres and 400 millilitres of rainwater.

The following week they collected three times more.

How much rain did they collect in the second week? Right, so your bar model should have looked like this.

So let's make sure that it's correct.

Well, we know that one of our parts because of what they collected in one week was three litres and 400 millilitres.

And we also know that it was three times more.

Okay, as you see that.

Now what we didn't know was our whole.

So what calculation are we going to get from this? when it comes to multiplication and division, when we don't know our whole, then we need to multiply one of our parts by the number of equal parts or by having much it says it was here.

So in this case three times more, okay.

So the calculation is three litres and 400 millilitres, times by three because it says three times more.

What do we do? We separate our like terms. And that would be three litres times by three and 400 millilitres times by three.

Oh, we've got 1200 millilitres again.

Now what do we do? Well, we know that 1200 millilitres is the same as writing it like this.

Which means we can then write it like this as one litre and 200 millilitres.

And then we bring it all together to get our final answer of 10 litres and 200 millilitres.

Right, really good work guys.

Let's go to the next one.

Right, so Judy, Hannah and Aliyah collected rubbish from the school field each day they were at school.

They collected five times as rubbish on Friday compared to Monday, five times less.

Remember what that would look like.

They collected 10 kilogrammes and 500 grammes of rubbish on Monday.

How much should they collect on Friday? So your bar model should look like this.

So let's just check while we know that our whole is equal to 10 kilogrammes and 500 grammes.

Okay, because that's how much they collected on Monday and that was the biggest amount.

We know that it was five times less than a Friday, which is why we put divided by five.

But what we don't know is one of our parts, which is what they collected on Friday.

And that's why it's a question mark there.

So what is our calculation? Well, when we know our whole and we don't know a part, then we need to divide.

Okay.

So in this case, it's telling us that we need to divide it by five, which is really nice and easy.

Right so here we go.

There's our calculation.

We separate our like terms. So we have 10 kilogrammes divided by five, which is equal to two kilogrammes, okay.

And 500 grammes divided by five, which is equal to 100 grammes.

We then put them together and we get an answer.

Two kilogrammes and 100 grammes, which is how much they collected on Friday.

And that's it guys.

Really good.

I'm really happy that we went over our bar modelling with addition, subtraction, multiplication, and division.

Remember as always, you always ask yourself those questions.

What do I know, what do I not know, and what is the question asking me to do? Okay.

Now remember with addition and subtraction, when you don't know the whole then you need to add the parts.

In addition and subtraction, if you don't know the parts, then you need to do whole, take away parts.

When we come to multiplication and division, when we don't know the whole, then we need to do the number of equal parts times by the value of one part.

When we don't know the parts, we need to do the whole divided by the number of equal parts.

Don't forget that.

Really good work.

Good luck with the rest of your learning today.

See you soon.