Lesson video

Hi everyone, nice to see you.

I hope you're all okay.

Today we're going to be creating bar models.

So if you can go and find a nice quiet place, ready to do some maths.

In today's lesson, we will be creating bar models to represent word problems then I'd like you to have a go at the worksheet and then a quiz.

For today's lesson, you will need a pencil, a ruler, and some paper.

Pause this video now to get this, if you have not got it already.

Here is a word problem.

Anna bought 11 red apples.

Joe bought eight bananas.

How many pieces of fruit did they both buy? What is known to us and what is the unknown? Now the big clue is that they are asking me what they both buy.

If it's what they both buy, I know the number is going to increase and my answer will be bigger.

So I know it's an addition question.

We know that one part is 11 because she bought 11 red apples.

We then know that the other part is eight because Joe bought eight bananas.

The whole is the unknown, and that's what we're going to solve.

Because I'm looking for my whole, my equation will be eight, 11 plus eight is equal to the unknown.

Now I understand what the problem is asking by using my bar model I can solve my equation.

11 plus eight is equal to 19.

Therefore they both bought 19.

Let's try this new word problem.

There were 17 bananas at the fruit stall.

Eight of them were green.

How many were yellow? What is known and what is unknown? The whole is 17 because there were 17 bananas.

But drawing 17 squares, it's going to take a really, really long time.

So what I'm going to do is just draw a long rectangle and label it 17.

Now in my question, it says eight of them were green.

So eight of those 17 bananas were green.

So I know that's one of my parts.

One part is eight.

So what I'm going to do, I'm going to split my bar into two parts and label one part eight, because that's known to me.

Now this second part here, is what is unknown as we need to find out how many of them are yellow.

How many of these 17 bananas were yellow? The bar model itself doesn't solve the calculation for me, but it helps me find out what I need to do.

So I can see that my equation will be, 17 take away eight is equal to the unknown because I know my whole and one part.

I can now solve this equation.

And I know that 17 take away eight is equal to nine.

Let's see if we can do this one together.

Have a go at drawing this bar model at the same time as me.

Have your pencil, paper and ruler ready.

The fruit seller has 67 carrots, but he sells 35 of them.

How many does he have still to sell? What is known to us? We know the whole is 67 because he starts with 67 carrots, but drawing 67 boxes will not fit on our piece of paper.

So we need to draw a long rectangle and we need to label this 67.

Have a go of this now.

Now it says he sells 35.

So if he's selling them, the number will get smaller.

So that is one of my parts.

Split your rectangle into two parts and label one part 35.

Now this second part here is what is unknown to us.

And that's what we need to find out.

So let's label this the unknown.

Pause the video now if you need to finish your bar model.

So again, the bar model itself doesn't solve the calculation for me, but it helps me find out what calculation I need to do.

So I can see that because I know my whole, and one part, it is a subtraction question.

My equation will be 67 take away 35 is equal to the unknown.

Pause the video now to see if you can work out the answer.

I know six take away three is equal to three.

So I know 60 take away 30 is equal to 30.

And I know seven take away five is equal to two.

30 plus two is equal to 32.

Therefore 67 take away 35 is equal to 32.

Let's see if you can try this one by yourself, just try your best.

There were 78 apples at the fruit store.

A customer bought 31 apples.

How many apples were left? Can you have a go at drawing this word problem as a bar model and solving the calculation? Have a think about what is known to us and what is the unknown.

Pause the video now.

We know the whole is 78 because it starts with 78 apples.

So we need to draw a long rectangle and we need to label this 78.

A customer bought 31 apples, so that is one of our parts.

Split your rectangle into two parts and label one part 31.

Now this second part is what is unknown to us and that's what we need to find out.

So let's label this, the unknown.

Does your bar model look like this? What will our equation be? That's right, 78 take away 31 is equal to the unknown.

Let's have a go at solving yet.

I know that seven take away three is equal to four.

So I know that 70 take away 30 is equal to 40.

Eight take away one is equal to seven.

40 plus seven is equal to 47.

Therefore 78 take away 31 is equal to 47.

Well done for having a go.

Now this bar model will be labelled slightly differently.

Let's see if you can work out why.

The fruit seller has 35 bananas in a box.

He adds 42 more.

How many bananas are there now? Now from this question, what is known to us and what is the unknown? We know the fruit seller starts with 35 bananas.

And we know that he adds more.

So that means we know the two parts, but we don't know the whole, the whole is unknown.

Because we know the two parts, but the whole was unknown, we will be adding.

That's why the question is different.

We will be adding and not subtracting.

Did you manage to work that out? First, I draw my bar because I know I will have two parts.

I label my first part 35.

He adds 42 more so that's my second part.

The whole is the unknown.

To work out the whole, I need to add my two parts together.

Three plus four is equal to seven.

So 30 plus 40 is equal to 70.

Five plus two is equal to seven.

70 plus seven is equal to 77.

Let's see if we can do this one together.

Have a go at drawing this bar model the same time as me.

Have your pencil, paper and ruler ready.

Amy bought 52 bananas, and David bought 31 bananas.

How many bananas did they both buy? We know Amy had 52 and David had 31.

We need to work out how many they both buy.

If we're working out how many they both have, that means we know the two parts and we need to work out the whole.

Can you have a go and draw this bar model? First, I draw my bar because I know I will have two parts.

I labelled my first part 52.

I then need to label my second part.

This is 31.

The hole is the unknown.

What will my equation be? That's right, 52 plus 31 is equal to the unknown.

Pause the video now to solve it.

52 plus 31 is equal to 83.

I know this because five plus three is equal to eight so 50 plus 30 is equal to 80.

Two plus one is equal to three.

80 plus three is equal to 83.

Let's do one final one before you complete your worksheet.

One customer bought 36 blueberries.

Another customer bought 22 blueberries.

How many blueberries were bought all together? Pause the video now to draw a bar model, to help you answer the question.

Don't forget to write your equation.

First, I draw my bar because I know I will have two parts.

I label my first part 36 and I label my second part 22.

Then we need to label the unknown part because that's what we're trying to solve.

Hands up if you remember to write your equation.

Fantastic, my equation is 36 plus 22 is equal to the unknown.

And the answer will be 58.

Have a go at answering these word problems. First, you need to read the question and work out what operation to use, whether is addition or subtraction.

I like to underline any key words or numbers in the question two.

Then draw your bar models and work up your answer.

Pause the video now, and then press play when you're ready for the answers.

A and B, C and D.

If you'd like to share your work with Oak National, please ask your parent or carer to share your work on Twitter, tagging @OakNational and #LearnwithOak.

You've done some great work today.

Let's see what you can remember.

So go and complete the quiz, well done.