Lesson video

Hello, my name is Mrs. Behan, and in this lesson, I'm going to teach you how to multiply numbers by 10 and 100.

Is that something that you think you can do already? Well, if not, then by the end of the lesson, you certainly will be able to.

And if there's something that you think you can do, join in with the activities I have planned to see if you really do know the secret of multiplying by 10 and 100.

Let's begin.

The ultimate goal of this lesson is to be able to multiply numbers by 10 and 100.

We will use our understanding of place value to do this.

I promise it will be nice and easy.

We will then look at written calculations where whole numbers are multiplied by 10 and 100.

By this point, we will have found the secret of this lesson, so we will use it to practise together.

Finally, you will be able to complete the independent task.

Of course, you will want to know how you got on.

So we will go through the answers together.

For this lesson, you will just need two things, something to write with, so a pen or a pencil, and something to write on.

If you haven't got those things handy, pause the video whilst you go and get them.

Try to work in a quiet place where you won't be disturbed.

Have you ever heard of Lewis Hamilton? He's a famous British Formula One race car driver.

On the TV, over 470 million people watched this sport.

And at the Silverstone circuit, which is the British racetrack, on one day in 2018, 135 thousand people went to watch the race.

Wow, I would say that's a pretty popular spot.

And having all of those zeros on the end of those numbers makes us understand just the size of the crowd.

It's absolutely huge.

Here is a picture of what might be seen as Lewis Hamilton races around the track.

There is so much maths going on here.

Maths can be seen in our daily lives, if we pay attention to it.

I know in this scene, I can see a clock, and patterns around the edge of the track.

Pause the video here and look to see what maths you can find.

When you are ready, come back to me.

Don't panic if you can only find a couple of things.

I'll share with you what else I have found.

Okay, so what did you spot? As I mentioned before, I noticed a pattern.

The edges of the track have been painted red and white.

We can also see the Union Jack flying, which has a pattern of colours on it.

Distance features here.

The racers have to do 52 laps of the track.

To make the race fair, all racers need to do 52 laps of the track, and the track itself is around five kilometres.

In total, that's around 260 kilometres.

If that was stretched out, I could get pretty close to London from where I live in Manchester.

Did you notice multiplication? Each racing car has got four tyres.

There are 20 cars on the track so I can multiply 20 by four to work out there are eighty tyres on the track.

I also noticed time.

There is a stopwatch timing the race.

By using this, it can be measured how long it took the racers to get around the track.

There will also be a set day, date and time for the race so that spectators can come and watch.

Do you remember we talked about 135 thousand people going to watch the grand prix on one day.

Racing fans use many forms of transport to get there on race day.

On race day, some people travel to Silverstone by motorbike.

A bike can carry one person to Silverstone.

How many people can travel to Silverstone on five bikes? We can use the multiplication five times one, or one times five, to work out that five people can travel to Silverstone on five bikes.

To help us get to the end goal for this lesson of multiplying by 10 and 100, we're going to use a place value chart.

I'd like you to watch what I do on this one.

I have five equal parts.

The blocks represent my bikes.

Each with a value of one.

Five multiplied by one is equal to five.

Not everybody travels to Silverstone on a motorbike.

Some people travel in groups and they go on a minibus.

Read this question with me.

A minibus can carry 10 times as many people as a motorbike.

So how many people can travel to Silverstone in five minibuses? Well, we first need to work out how many people fit on one minibus? So if one person fits on a motorbike and 10 times as many people fit our minibus, we know that 10 people can travel on a minibus.

So to work out how many people can travel in five minibuses, we need to use this calculation.

10 multiplied by five.

So we know that the same number of minibuses can take 10 times as many people to Silverstone.

Here I am changing my ones for tens, because 10 people can fit on a mini bus.

One, two, three, four, and five.

I have made each part 10 times greater, but what is wrong with my representation? I'm sure you noticed that the tens have a column of their own and all of those should be in the tens column.

Let's sort it out.

Okay, so I'm going to move them over.

One, two, three, four, and five.

Five multiplied by 10 is equal to five.

Wait, does that sound right? What have I forgotten to do? Of course we count these in tens because these are in the tens column.

I'll have another go.

Count with me.

10, 20, 30, 40, 50.

Good job.

Now, how can we explain the calculation using parts and wholes language? So we can say there are five equal parts each with a value of 10.

Five multiplied by 10 is equal to 50.

I just want to remind you that the Dienes blocks are just a way of representing the calculations and you shouldn't really need to count the blocks to calculate the product.

I know that you already know the multiplication facts for the five and 10s times tables.

And when we know the facts, we should be using those.

What would our representation look like if we made each 10, 10 times greater? Let's have a look.

So each 10 has been replaced by a 100 block.

That's because each 10 has been made 10 times greater.

We started with five tens, which is 50 multiplied by 10 is equal to 500.

Okay, quick pause point here.

Have a look at the cards on the screen.

One of them shows us false information.

Pause the video and try to figure out which one it is.

I'll give you 50 points if you can get it right.

So have you earned your 50 points? The first pink box says 50 is 10 times greater than five.

So we need to imagine five ones, then multiply by 10, giving us 50.

So that's correct.

Let's go down to the green box.

500 is 10 times greater than 50.

We know that 50 multiplied by 10 is 500.

We saw that earlier.

Read the purple box with me.

500 is 10 times greater than five.

Is that right or wrong? That's wrong.

We know that five multiplied by 10, to make it 10 times greater is, 50, not 500.

I thought the blue box might've thrown you out.

50 is 10 times smaller than 500.

It was a bit of a challenge, that one.

If we had five 100s, and we made them 10 times smaller, we would have five tens and five tens are 50.

So that's correct too.

For this next part, I'd like you to draw a place value grid, unless you have Dienes blocks and a chart at your house.

I made my own place value chart at home.

You could do this too.

You just need pencil and paper.

It doesn't need to be a big like mine because you will draw a few of these later on.

Mine's just large so you can see it.

Okay, so you're going to use your place value chart now.

I'm showing you this number.

This is number six.

This is how you represent six on your place value chart.

Here's mine.

I have represented six.

There are six equal parts and the value of each part is one.

Six multiplied by one is equal to six.

Why don't you have a go on your place value chart.

Do you think we can multiply by 10 again? Pause the video and have a go.

How did you get on? Here's my place value chart.

So you can see, I crossed out my tens and I moved them across and made six 100s.

Let's say this sentence together.

Sixty multiplied by 10 is equal to 600.

600 is 10 times greater than 60 and 60 is 10 times greater than six.

The calculation we can write to show our representation up here, is 60 multiplied by 10 is equal to 600.

You can see we've got two zeros as placeholders because we have six 100s, zero tens and zero ones.

So I said earlier that we were going to try and find the secrets of this lesson.

So I'm going to show you the calculations that we have used so far.

Look carefully at the calculations and see if you can spot what the secret might be.

Your might want to pause the video whilst you have a little think.

Did you manage to find the secret? You can see that we have used lots of zeros here.

The zeros today have been used as placeholders, and it's important to use them to show that there are zero ones.

If we didn't use the zeros as placeholders, it would look like the answer to all of these questions, or the product, would just be five.

And the products of all of these questions would simply be six.

So we need the placeholders to show the correct value of the six in this question and the five in this question.

So let's practise what we've learned so far.

Can you copy out these sentences and fill in the missing words? I'll read them to you: When multiplying a whole number by 10 or 100, we use something as a place holder.

To multiply a whole number by 100, you can multiply by something then by something again.

When you've worked it out, come back to me.

So here are the answers.

Can you say them with me? I'm sure you've got these right.

When multiplying a whole number by 10 or 100, we use zero as a place holder.

To multiply a whole number by 100, you can multiply by 10, then multiply by 10 again.

Are you ready to whiz through some questions on your own now? See if you can have a go at these.

There's some missing numbers to fill in here, followed by true or false statements.

And then there's a little bit of a word problem.

I'm sure you're keen to see how you got on.

So let's go through the answers together now.

Seven multiplied by one is equal to seven.

I looked at this question next, because I noticed it had a connection to this first calculation here.

Seven multiplied by 10 is equal to 70.

I made the seven 10 times greater and I used zero as a placeholder.

Seven multiplied by 100 is equal to 700.

I use two zeros here, because there are zero tens and there are zero ones.

Nine multiplied by one is equal to nine.

Nine multiplied by 10 is equal to 90.

Nine multiplied by 100 is equal to 900.

True or false: three multiplied by 10 is 300.

That one's false.

Three multiplied by 10 is just 30, not 300.

Five made 10 times greater is 50.

That one's true, and I think we saw that calculation earlier in our lesson.

Six multiplied by 100 is 60.

That one is false.

Six multiplied by 10 is 60.

If we multiply 60 again by 10, then we get 600.

So six multiplied by 100 is 600, not 60.

Zoe could name eight animals.

Ben could name 10 times more animals than Zoe.

How many animals could Ben name? Ben could name 80 animals.

We're now coming to the end of this lesson.

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

Thanks for taking part in this lesson.

I hope you've enjoyed it as much as I have.

Don't forget to take the quiz to test out your new learning.

Hope to see you again soon.

Bye bye.