Lesson video

Hello, My name's Miss Thomas.

I'll be going through the lesson with you today.

We're doing a lesson on multiplication, consolidating lots of strategies, so I hope you're ready for an exciting lesson ahead.

Let's begin.

In today's lesson agenda, we're going to be doing a consolidation lesson on multiplication.

First, we'll be exploring the associative law of multiplication, then we'll go to a talk task where you'll be spotting the mistakes in short multiplication.

After that we'll be exploring when mental or written methods are most efficient when solving multiplication problems. And finally, we'll have our end of lesson quiz, where you can test yourself in the lessons learning.

For today's lesson you're going to need: a pencil, paper, and a ruler.

Pause the video now and gather your equipment if you haven't done so already.

Let's begin.

We have a new star phrase.

My turn, associative law.

Your turn.

Associative law means multiplication factors can be solved in any order and the product will be the same.

The answer will be the same.

You've got a task to do here.

Number one, choose three digit cards.

Two, arrange them in calculation.

Three, how many different calculations can you make using your three digit cards? Four, which order do you find the most efficient to solve, to calculate your product? Pause the video, and have a go at this task.

Welcome back! You should've found that there were six different orders you could put your, you could calculate your problem in, and you should've found that maybe, when you were having a practise of which order you find the most efficient, perhaps, sometimes having the greater numbers first made it a bit easier, because then we don't have to multiply greater numbers with the two digit number at the end? Or perhaps you like to keep what numbers like, one, two, and four till the end, because they're easier to multiply by mentally.

It's great that you've had a chance to explore the most efficient order to calculate in.

Next, you're going to make the target number of 48 using three of the digit cards below, And have a think, can you complete this problem in more than one way? Pause the video and have a go.

Welcome back! Here are the answers, hopefully you found you could find the product 48 in more than one way.

Next, we're at the talk task.

Here are three incorrect equations.

Spot the mistake, explain where the person went wrong, and correct them.

Pause the video now to complete your talk task.

Here are the talk task answers, where the mistakes have been corrected.

Hopefully, you had a chance to explain out loud, where these individuals went wrong, and had a chance to correct them.

Next, we're going to explore the Distributive law.

That's our new star phrase.

My turn, Distributive law.

Your turn.

Distributive law means to reach the same answer when parts are solved separately.

This is something we a lot when we solve calculations mentally.

So here, I have an area model and I'm going to calculate 212 multiplied by six.

Here 212 can be partitioned into 200 and 12.

We could calculate 200 multiplied by six first, so I need six groups of 200.

So that's my second group, third group of 200, fourth group of 200, fifth group of 200, and sixth group of 200.

My calculation would be 200 times six.

Which I know that two times six is 12.

I know that 200 times six would be 100 times greater, so it would be one part equal to 1200.

Next, I can do 12 multiplied by six, so I've already got my first group of 12 on top so I need my second group of 12, my third group of 12, fourth group of 12, fifth group of 12, and sixth group of 12.

This gives us a calculation of 12 multiplied by six.

Which I know is equal to 72 using my known facts.

The final step is to add the two products.

1200 plus 72 which is equal to 1272.

So, I know that 212 multiplied by six is equal to 1272.

This can be a useful method when we don't have to regroup.

When we need to regroup sometimes using other methods like short- multiplication method, can be more useful.

Here we have six multiplications.

You've got two questions.

Which of the multiplications would you calculate mentally? Which of the multiplications would you use a written method for? You can have a go at solving them, and then explain out loud to the screen your thinking.

Which would you solve mentally, which would you solve with a written method and why? Explaining out loud.

Pause the video now and have a go.

Welcome back.

You might have said that the equations where there were less or no regroups are easy to do mentally.

If there are multiple regroups it can be efficient to use the short multiplication method.

You may have found when timesing by four you could double, then double again.

Perhaps you found when multiplying by nine you could times 10 and then take away one group to have nine groups.

Well done for explaining out loud to you screen.

Here Leanna's made a mistake.

Can you explain her mistake out loud and correct the diagram? Pause the video to have a go.

Okay lets have a look at Leanna's mistake, corrected.

So Leanna has calculated 29 multiplied by four.

Leanna's done 30 multiplied by four is 120, and then 120 take away one is 119.

Finally, she's done 29 multiplied by four, she thinks is 119.

Let's go through it and see if you spotted her mistake like me.

So, Leanna thought it'd be easier to do 30 times four which is equal to 120 because 29 is one group away from 30, and multiplying by 30 is easier.

But then what Leanna didn't do, was she needed to do 120, so to take the answer and take away one group of four.

Not take away 1.

So as you can see on my diagram, I've corrected it, and I've taken away one whole group of four, so then by my calculation, my answer would be 29 multiplied by four is equal to 116.

You've reached your independent task.

You need to draw a bar model to represent the word problems. Pause the video to complete your independent task.

Let's take a look at the answers.

Each archer fires three arrows at the target.

There were eight archers.

How many shots were fired altogether? So we're trying to find the whole, how many shots were fired altogether? Each archer fired three arrows, there were eight archers.

So, I've got my eight equal groups, and the value of each group is three.

Let's take a look at number two.

Friar Truck had eight gold coins to buy food for the whole gang.

The sheriff had three times as many gold coins for himself.

How many gold coins did the Sheriff have? So the whole is how many gold coins the Sheriff had.

That's what we're trying to find out.

Friar Truck had eight gold coins.

The Sheriff had three times as many, so we need, three equal groups of eight.

That's what my bar model represents.

Maid Marian challenged the Sheriff to a race.

She ran round the course in eight seconds.

It took the Sheriff three times as long.

How long did it take the Sheriff to finish the race? So the whole is how long it took the Sheriff to finish the race.

So we need to do eight times three.

And, it took, she ran around the course in eight seconds, so I've got one bar of eight and I need the whole is three times the size of the bar with a value of eight.

Now it's time for you to complete your quiz and test yourself on your multiplication knowledge.

If you'd like to share your work with Oak National, please ask your parent or carer.

On Instagram, Facebook, or Twitter tagging @OakNational and #LearnwithOak.

And we've reached the end of the lesson, well done.

There was so many different tasks within this lesson, where you had to explore different multiplication strategies.

So you've done really well with a lot of work, so well done to you, give yourselves a pat on the back for that one.

See you next time.