Lesson video

Okay, so welcome to our next lesson, and we will be using bar models to represent measurement problems. So let's get started.

So our lesson agenda, first we're going to be matching bar models for non-standard contexts.

Okay.

That means we're not going to be using any units, and we're going to be identifying the correct calculations for a bar model, which will then prepare you for your independent task, where you complete it and then come back to the slides to do the answers with me.

All right.

So what you will need today is a pencil and a ruler to do incredible bar models.

You also need a rubber for any mistakes that you may do, and an exercise size book to put in all your fantastic work.

Right.

So let's start by reading the word problem.

Mr Slade shared out the felt tip pens fairly so that each of the four tables had 12 pens.

How many pens did Mr Slade start with? So what do we know? Well, we know that there's four equal groups.

So that means there's four equal parts.

And we know that the value of each part is going to be 12.

What we don't know is our whole.

So the relationship between the known and the unknown values are that there's four equal parts.

We know that each part is equal to 12, but we do not know our whole, therefore our bar model will look like this.

Now that's what we do in last lesson.

We're now going to connect that to calculations.

We have these three options here, 12 divided by four, 24 divided by two, or four times 12.

Now we need to think about which calculation goes with this bar model.

Now let's have a look at the bar model.

Okay.

So we know that if one part is equal to 12, in order to get our whole, we need to have, one 12, two twelves, three twelves, four twelves.

So instead of saying 12 plus 12 plus 12 plus 12, we can say 12 times four or four times 12.

Okay.

Which is why this is the correct calculation.

Well done guys.

Next time I want you to help me.

Let's go.

Read question first.

Hannah had 12 marbles.

She gave the same amount of marbles to her four friends.

How many marbles each of them receive? Okay.

So same questions.

So we know that there is four friends.

So that must mean there's four equal groups.

Okay.

And we know that the whole is equal to 12.

So we know the whole, we know there is four equal groups, but what we don't know is the value of each part.

So let's have a look.

Our bar model should look like this, where we again, we know the whole is 12.

We know there's four equal parts, but we don't know the value of one part.

So what is going to be our calculation? Well.

when we're trying to figure out, the value of a whole, as we know, when we're finding out the value of our whole, then we normally divide it by the number of equal parts.

Okay.

And how many equal parts do we have? We have one, two, three, four.

So it'd be 12 divided by four, will give us this answer.

So in that case, we know that this is the correct calculation, 12 divided by four.

And 12 divided by four is equal to three.

Well done guys.

Let's go to the next one.

Pierre was fishing on Monday and Tuesday.

He caught 24 fish on Tuesday, which was twice as much as Monday.

How many fish did he catch on Monday? Well, what do we know? We know that he caught 24 fish on a Tuesday.

Okay.

And we knew it was twice as much.

And I remember in the last lesson, when we say twice as much, that means that we're multiplying.

Okay? What do we not know? Well, we don't know the value of one part.

And that's Monday in this case.

So our bar model should look like this.

Okay.

Where our whole is 24.

Okay? We know that it's twice as much, which is why this is times by two.

Okay? And the unknown is our one part.

Which is Monday.

Which is right here.

So what is our calculation? Okay.

So we have 12 divided by four, 24 divided by two and four times 12.

In order for us to get this part here, we need to look at this arrow right here.

It says times by two.

But we want to find out what it is going this way.

And what is the inverse of multiplication? That is division.

So instead of times by two, we're going to divide it by two.

So to get out one part, we need to divide our Whole by two.

So therefore the correct calculation be, 24 divided by two, which is equal to 12.

The reason I know that, is because I know two times 12 is equal to 24.

Therefore 24 divided by two is equal to 12.

Right.

Well done.

I think is time for you guys to have a go.

So Mr Nieto shared out the felt tip pens fairly so that each of the five tables had eight pens.

How many pens did Mr Nieto start with? Think about those questions.

What do we know? What we don't know? Okay? So what are you going to do first, you're going to pause the video and you're going to match the word problem to the bar model.

Okay.

So let's come back.

So in that case, our answer should be.

Option two.

Well done.

And that is our bar model.

Okay? So what do we know? Well, we know that the one part is equal to eight, we know that there are five equal parts here.

And what we don't know is our whole.

And that's why this is our bar model.

Next part.

Well.

Now that we know our bar model, I now want us to choose the correct calculation.

So you're going to pause the video and do that for me now please.

Okay.

Back to me.

Ready? Answer is.

Option number one.

Okay.

And how do we know that? Well, remember when we're trying, when we don't know the whole, then we multiply the number of equal parts, which is five by the value of one part, which is eight.

So it'd be five times eight.

Which is option number one.

Okay.

Let's move on to the next part.

Well done guys.

So we're going to be identifying the correct calculations for a bar model.

Okay.

So on Tuesday, Mr Slade gave out twice as many house points as he did on Monday.

Twice as many.

Remember these words.

He gave out 24 and Tuesday.

How many did he give out on Monday? Twice as many.

Remember that.

So what do we know? Well, we know that he gave out 24 on a Tuesday.

So that means that's our whole.

We know our whole is equal to 24.

We also know that it was twice as many.

Okay.

Compared to the Monday.

What we don't know is the value that he gave out on Monday.

Right? So that's why I put in twice as many because it's times by two.

So our bar model should look like this right here.

Okay.

Now what is the calculation from this? So again, if we do not know the parts, then we divide.

If we do not know the whole, then we times.

That seems to be our rule.

So do we know our parts? No.

So what do we need to do? We need to divide.

We need to divide 24 by what? By two.

Good.

Because we know that we have the arrow going this way.

That means the opposite.

Okay.

And the inverse or the opposite of multiplication is division.

So the calculation would be, 24 divided by two, which should give us the Monday value, which is 12.

All right.

I need you guys to help me for the next one, please.

Now that Easter is over, Ali eats three times fewer chocolate buttons each day.

Each day, he now needs 12 buttons.

So when it was Easter, he ate three times as much as he eat each day now.

Okay.

How many was he eating each day when it was Easter? So during Easter, he ate three times as much as he eats now.

Remember that.

I think the wording here is really difficult and sometimes it can be.

And the most important thing is when you come across a word problem and it's a little bit tricky, just relax and go through the steps.

What's the first one.

I know I can hear it from the computer.

What do we know? So we know that each day was 12 buttons.

Okay.

That's how much he is eating now.

That's how much he's eating now.

We also know that he was eating three times fewer.

Fewer is the same as three times less, which we know is dividing by three.

Okay.

Three times fewer, three times less divided by three.

What do we not know? what We don't know is whole.

We don't know how much he ate during Easter.

So we know our parts.

We know that it was three times fewer.

Okay.

But we don't know the whole.

So our bar model should look like this right here.

So how do we get our calculation? Well, remember if we know the parts and we don't know the whole, then we need to multiply.

If we don't know the parts and we know the whole, then we need to divide.

So what do we know? We know the parts and if we don't know the whole, we need to multiply.

Really good.

Okay.

And what do we need to multiply with and what are we multiplying? Well, we need to multiply the value of one part by the inverse of this.

What's the inverse divided by three? Times by three, or multiply by three.

So the calculation here is, 12 multiplied by three, which gives us 36.

Good work guys.

Let's go to the next one.

Okay.

Your turn.

Right.

Excited.

Really excited about this.

Addy and Melvin volunteered to give out the fruits for Mr. Slade.

They put a bag of six apples on each table.

So they went around.

Okay.

On each table.

Bag of six apples.

If there are five tables, Okay.

How apples were there altogether? Now, there's key words there.

What do we know? Okay.

Do we know the parts? Do we know the wholes? Okay.

Do we know how many equal parts there are? And in terms of the calculation, remember when we don't know the whole, then we need to multiply the equal parts by the value of one part.

If we don't know the part, then we need to divide the whole by the number of equal parts.

Good luck.

Come back when you're finished.

Okay.

I'm excited about this one.

So the right calculation is.

option number three.

Excellent.

Now the reason why, let's have a look.

We're going to go through this together.

So we know that there are five equal parts, which I have my five bar models there.

We know that the one part is equal to six.

Okay.

And what we don't know is what it is altogether.

Which is our whole.

So we don't know our whole, we know how many equal parts and we know the value of each part.

So the bar model should look like this.

Remember if we don't know the whole, then we need to multiply the value of one part by the number of equal parts.

So therefore, how many equal parts do we have? one, two, three, four, five.

That would be five times six, which gives us 30.

Good work guys.

Really impressed.

I think you guys are ready to go with your independent task.

Here it is.

You have four problems to do.

What I like you to do now is to pause and go into the worksheet and to complete it in your exercise book.

Remember those steps, What do we know? What do we not know? Okay.

That helps us to draw a bar model, and then we can use our bar model to get our calculation.

If we don't know the whole, then we multiply the equal parts by the value of one part.

If we don't know the parts, then we divide the whole by the number of equal parts.

Okay.

Remember that when we say, was two times bigger or three times bigger, means we're timesing.

And when we say that it's three times less or three times fewer, that means that we are dividing.

Remember, look out for those key words.

Right.

Good luck.

Come back to when you're finished.

I'll be waiting right on here.

All right, guys.

Looking forward to this.

Here we go.

So question number one.

Buttons shared his chocolate buttons with friends in his class.

10 friends each got 50 grammes of chocolate buttons.

What was the total weight of the buttons that Buttons gave to his friends? Uh! Hello buttons there again.

Buttons, buttons, buttons.

So what do we know? Always ask ourselves that.

We know that there's 10 friends.

So therefore there's 10 equal groups.

We know that each got 50 grammes.

That means that each part will be equal to 50 grammes.

What we don't know is the total weight.

So we know our parts, we know the number of equal parts, but we don't know our whole, so our bar model should look like this.

Okay.

Well again, just highlight that.

We know that the 10 friends equals technical parts.

We know that one part is equal to 50 grammes.

And what we don't know is our total weight.

So what does that calculation? Remember if we don't know the whole, then we need to multiply the number of equal parts, One, two, three, four, five, six, seven, eight, nine, 10, by the value of one part, 50.

So the calculation will be 50 grammes times by 10, which is equal to 500 grammes.

which on a challenge, what is 500 grammes? Is half of one kilogramme.

Just check it.

It's okay if you didn't get that.

It's challenge question there.

Next one, Melvin measured the height of the sunflowers every day.

In one week his sunflower grew only half as much as Addy's.

Melvin sunflower grew 35 centimetres.

How many centimetres did Addys sunflower grow by the week? Well, what do we know? So is, what do we know? What do we know? That's what I keep asking myself.

What we it's in one week, it grew half as much.

Okay? We also know that it grew by 35 centimetres.

And what we don't know is, is what was the height of Addys.

So in that case, our bar model should look like this.

Where we know the value of one part.

We know that it says half as much.

Okay.

So half as much is I say in two times less, which means that we're dividing by two and we don't know Addy's value, which is the whole.

Okay.

Remember if we don't know the value of our whole, we need to multiply the value of the one part by either the number of equal groups or in this case, the inverse of what's happening here.

And the inverse of divide by two is times by two.

So it will be 35 centimetres times by two, which is equal to 70 centimetres.

Good work guys.

Let's go to the next one.

Okay.

Addie and Melvin collected three times as many cans in July, as they did in June.

They collected three kilogrammes and 900 grammes of cans in July.

What was the weight of the cans collected in June? So we know that there are three times as much.

Okay.

So I know I'm going to be times of my three.

I know that there were three kilogrammes of 900 grammes.

So that means that it's my whole.

And what we don't know is the value of one part in June.

Okay.

So our bar model should look like this.

Where we know our whole are three kilogrammes and 900 grammes.

Okay.

We know that it is three times as much, which is why the arrows is there like this, or I suppose three equal parts.

And what we don't know is our parts.

Remember if we don't know our parts, then we need to divide the whole by either the number of equal parts or the inverse of times by three.

So what's the inverse of times three? Divided by three.

So therefore our calculation will be, three kilogrammes and 900 grammes divided by three.

Right.

We're going to go back to what we learned last lesson, when we were dividing using mixed units.

So what do we do first? We group our terms. Okay.

So three kilogrammes divided by three is equal to one kilogramme and 900 grammes divided by three is equal to 300 grammes.

I know that because nine divided by three is equal to three.

So 900 divided by three is equal to 300 grammes.

And then finally we put them together and that's one kilogramme and 300 grammes.

So that's how much they collected in June.

Right next one, Mr Slade poured out the last of the juice by filling up one cup of juice each for the three moles.

If they each got 250 millilitres of juice, how much did Mr. Slade pour out altogether? All right.

So what do we know? I know that there are three moles.

That means there's going to be three equal parts.

I know that they each got 250 millilitres.

That means that each part is equal to 250 millilitres.

And what we don't know, what we're looking for is our whole.

Okay.

So your bar model should look like this and let's just double check that.

Yeah.

Three moles equals three equal parts.

So 150 millilitres is equal to the one parts.

And what we don't know is our whole right there.

So what is that calculation? Here we go again.

If we don't know the whole, then we need to multiply the number of equal parts, which is one, two, three, by the value of one part, 250.

So your calculations should be 250 times by three, which gives us 750 millilitres.

Great work guys.

Really, really good.

Remember, there's a pattern that we follow when we go through this.

It can be tricky, but with practise, you will get better.

I can't wait to see how you got on.

Keep working hard and I'll see you in the next lesson.

Good luck.