Lesson video

Hello, and welcome to today's lesson about using the multiplication symbol.

My name is Miss Sabzvari, and I'm very excited and happy to meet you all.

So, when you're ready, let's begin.

On the lesson agenda for today, first we're going to be introduced the multiplication symbol.

Then, we're going to complete our talk task by creating some arrays.

Next, we will be interpreting some arrays.

And finally, you will complete your independent task.

Before begin the lesson, you will need the following items: You will need something to write with and something to write on, and you will need some counters or cubes.

Alternatively, if you don't have any counters or cubes, please ask your parents or carer to cut out some small pieces of paper that you can use instead.

Multiplication symbol.

The cook is preparing school dinners.

A tray can hold four rows of five sausages.

How many sausages can fit in one tray? What I would like you to do is to work out how many sausages are on that tray? Good work.

There are 20 sausages on that tray.

But how did you count the sausages? Pause the video now and share your answer out loud.

Well done.

You may have counted your sausages in ones, by going one, two, three, four, five.

Which would have been time consuming.

Or, you could have counted them in columns.

Like saying four, plus four, plus four, plus four, plus four.

So counting them in columns.

Or, you may have counted them in rows Five, plus five, plus five, plus five, because there are five sausages in each row.

We could also say, that although we can write the repeated addition equation, we can also show this diagram and write this using the multiplication symbol.

We could say that there are five columns.

So one, two, three, four, five, columns of four because there are four sausages in each.

Or, we could say that there are five equal groups of four.

Five equal groups of four.

And we could say that there are four rows of five, as we mentioned.

Or, we could say that there are four equal groups of five.

Because there are one equal group, two, three, four, so four equal groups of five.

Because there are five sausages in each group.

What I would like you to do now, is I would like you, to using your piece of paper and your pen or pencil, to write down the repeated addition equation and the multiplication equation for each diagram.

Do that now.

Good job! So having a look at the multiplication equations that you have had a go at writing down, what's the same and what's different? Pause the video now and share your answer out loud.

What's the same and what's different? Well done.

We can state that in both equations, there is a multiplication sign.

So that's the same, another thing that's the same, is that both of the equations are using the numbers five.

And they are using the numbers four.

However, what's different is that the numbers are the opposite way around.

This equation starts with five multiplied by four.

And this equation starts with four multiplied by five.

We can say that both of these equations, we will get the same answer because five multiplied by four is equal to 20.

And, four multiplied by five is equal to 20.

This means that multiplication is commutative.

My turn, your turn, commutative.

Well done.

That means that either way, the answer is still going to be 20.

Creating arrays.

The cook is preparing school dinners.

A tray can hold five rows of three cookies.

How many cookies can fit in one tray? Now I'm going to show you how I am going to create my arrays for this word problem.

I know a tray can hold five rows of three cookies.

Therefore, I will make an array with five rows.

One, two, three, four, and five.

Each row is going to have three counters to represent three cookies.

There are 15 cookies in total.

Let's count them together.

Three, six, nine, 12, and 15.

I could write a repeated addition equation for this array.

I could write three plus three plus, three plus, three plus, three is going to be equal to 15.

Or, I could write a multiplication equation for this array.

There are five groups of three.

So I could say that there are five equal groups of three.

That is going to equal to 15.

Now it's your turn.

Create an array to represent the word problem.

A tray can hold two rows of four fish fingers.

How many fish fingers can fit in one tray? Pause the video to complete your task.

Let's go through the answer together.

I know that a tray can hold two rows of four fish fingers.

Therefore, I will make an array with two rows.

One, Two.

And in each row, there are going to be four counters to represent the four fish fingers.

Three and four.

One group of four, two group of four.

I can say four plus four is equal to eight.

And I could also say that there are two groups of four.

There are two equal groups of four, and that is equal to eight.

Well done, if you got that correct.

Interpreting arrays.

Now that we know how to create our own arrays, we are going to try and interpret them.

How else could the cook arrange the 20 sausages? Remember at the beginning of the lesson, when we arranged the 20 sausages and they were in groups of four or five? Can you come up with a different way of arranging the 20 sausages? I can arrange the sausages in groups of two and each row of my array will have two sausages.

So two, four, six, eight, 10, 12, 14, 16, 18, and 20.

I still have 20 sausages in total.

And I can describe this as two plus two, plus two, plus two, plus two, plus two, plus two, plus two, plus two, and plus two.

So, which is all going to equal to 20.

I can describe this as 10 groups of two, and I can write this as there are 10 groups.

One, two, three, four, five, six, seven, eight, nine, 10, equal groups of two.

And that also equals to 20.

Each column of my array has 10 sausages.

So I could even look at the columns instead of the rows.

So each column, of my tray is going to have 10 sausages.

So I can describe this as 10, plus 10 is equal to 20.

There are two groups of 10, and I can write this as two equal groups of 10.

Or, two multiplied by 10 is equal to 20.

Remember multiplication is commutative.

That means that I can also write 10 multiplied by two, or two multiplied by 10.

Now we're going to move on to independent task.

The school cook has 12 cakes.

How many different ways can she arrange them? Pause the video and complete your task.

Remember to write down the repeated addition and multiplication equation for each of your arrays.

Once you are ready, we will go through the answers together.

I can arrange the cakes in groups of two, each row of my array will have two cakes.

Two, four, six, eight, 10, and 12.

I still have 12 cakes in total.

And I can describe this as two plus two, plus two, plus two, plus two, and plus two.

Two plus two, plus two, plus two.

One, two, three, four, five, six.

One, two, three, four, five, six.

And it will equal to 12.

There are six groups of two, and I can write this as six groups of two is equal to 12.

Each column of my array, has six cakes.

So if I now look at the columns, each column has six cakes.

Six, 12.

I can describe this as six plus six equals 12.

Or, is equal to 12.

There are two groups of six.

I've got two equal groups of six, and I can write this as two multiplied by six is equal to 12.

Remember multiplication is commutative.

That means it does not matter which way we write the numbers.

I can have six multiplied by two, or I can have two multiplied by six.

I can also arrange the cakes in groups of three, each row of my array will have three cakes.

Three, six, nine, and 12.

I still have 12 cakes in total.

I can describe this as three, plus three, plus three, plus three, is equal to 12.

I could say that there are one, two, three, four groups of three.

And I know that four groups of three is equal to 12.

I could also, instead of looking at rows, I could look at the columns.

There are one, two, three columns.

And in each column there are one, two, three, four cakes.

So, four, eight, 12.

And I can describe this as four plus four plus, four, is equal to 12.

Or, I can say that there are three groups of four.

Three groups of four, and that is equal to 12.

Remember that multiplication is commutative.

That means I can either say four multiplied by three is equal to 12.

Or I could say that three multiplied by four is equal to 12.

It's now time for you to complete your end of lesson quiz.

Pause the video here and do that now.

Great work, everyone! This lesson we learned that multiplication is commutative.

Next lesson, we will explore this further.

And one last thing from me, if you'd like to please ask your parents or carer to share your work on Twitter, tagging @OakNational and #LearnwithOak.