# Lesson video

In progress...

Hi everyone, I'm Miss Mitchell and today we're going to be representing information in a bar model.

In today's lesson, we'll be solving addition worth problems, solving subtraction 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 and some paper, pause this video now to get this, if you have not got it already.

Here's a word problem.

John picks apples from his garden, he picked three red apples and two green apples.

How many apples did he pick all together? How could I represent this word problem in a part whole model? What's the values of my parts.

The value of one part is three because John has three red apples, and the other part is two, because he had two green apples.

The whole is the unknown.

This means we don't know what the whole is and that is what we have to find out.

I can write this as an equation.

The equation is three plus two is equal to the unknown.

Here you can see how we get the answer to this equation because the whole is made up of three red apples and two green apples.

Altogether that are five apples.

As three plus two is equal to five.

We can represent the mass in the word problem, using another representation, a bar model.

Just like in the part whole model, the value of one part is three, and the other part is two.

I know by looking at this bar model, that three plus two is equal to five.

Let's try one together.

John picked apples from his garden.

He picked three red apples and four green apples.

How many apples did he pick all together? What are the values of my parts and what is the unknown value? Pause the video and have a think.

The value of one part is three, and the other part is four.

The whole is the unknown value.

Can you write this as an equation.

Three plus four is equal to the unknown.

Here again you can see the bar model.

One part is three and the other part is four.

And the whole is the unknown.

I know now by looking at my bar model, that three plus four is equal to seven.

Let's try a new one.

John picked 12 apples from under one tree and six apples from another tree.

How many apples did John pick all together? Can you have a go at this one by yourself.

Pause the video and have a go.

And here is the bar model.

The value of one part is 12, and the other part is six.

I know by looking at this bar bar model that 12 plus six is equal to 18.

A great job.

Now this word problem is a little bit different.

Let's see if you can work out why.

John brings in five apples in a basket and places two on the chopping board.

How many are left in the basket? How can I represent this work problem in a part whole model? What are the values of my parts? The value of my hole is five because there are five apples, one, two, three, four, five.

One part is two, because he places two on a chopping board.

As you can see, this is taken from the whole.

The other part is the unknown value.

And this is what is left in the basket.

This means we don't know what the part is and that's what we have to find out.

Could you work up why this question is a little different? Its because we are subtracting, I can write this as an equation.

The equation is five take away two is equal to the unknown.

We can represent the subtraction word problem using a bar model too.

Just like in the part whole model, the value of the whole is five.

And the part is two.

I know by looking at this bar model, that five take away two is equal to three.

Let's try another one together.

John and Anne an apple pie.

They chop six apples.

Anne chops four of them.

How many are left for John to chop? What is known to us and what is the unknown value? The value of my whole is six, and one part is four.

This four is taken from the whole and that's why it's subtraction.

The other part is the unknown value.

Can you mark this as an equation? The equation is six subtract four is equal to the unknown.

Can you represent the maths in the word problem, using a bar model.

pause the video now and have a go.

Here's what your bar model should look like.

The whole is six and one part is four.

So your equation is six take away four, which is equal to two.

Can you try this one by yourself.

When John brought his 18 apples into the kitchen, he saw that seven of them were bruised.

How many apples were not bruised? Pause the video, draw your bar model and write your equation.

Here's what your bar model should look like.

The whole is 18, and one part is seven.

The other part is the unknown.

Therefore, your equation is 18 subtract seven is equal to the unknown, and I know the 18 takeaway seven is equal to 11.

Have a go at answering these word problems. First, you need to read the question and work at what operation to use.

I like to underline any key words or numbers in the equation, then draw your bar models and work out the answer.

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