# Lesson video

In progress...

Hello everybody, my name is Ms. Hughes, and welcome to today's session.

In today's lesson, we're going to be exploring adding and subtracting multiples of ten.

So let's get going.

Let's have a look at our lesson agenda for today.

So we're going to start off, by adding multiples of 10, then you're going to have a talk task, next, we're going to think about subtracting multiples of ten.

And finally, you're going to have a main task and a quiz to complete.

For this lesson today, you are going to need a pencil and a rubber and some paper.

So pause the video now to get these things if you have not got them already.

Brilliant.

To start us off today, I want you to have a go at writing these numbers in words.

The first one has been done for you.

You can pause the video here, if you need a bit of time to do that.

Great job team.

Let's go through these answers.

So the first one is fifty eight.

The next one is forty six, twenty four, thirty one, thirteen, and eighty eight.

Make sure you've checked those spellings as well.

It's so important that we're getting those spellings for each number correct.

Okay.

Let's get started.

So, in the first part of our lesson we're going to be thinking about adding multiples of 10.

So let's have a look at this question on the board.

Benches can hold ten people.

How many people can fit on these benches? Well, if I have a look at my image, I can see I've got some benches here.

I can see that there are four benches.

So if ten people can sit on each bench, I can count my benches in tens 10, 20, 30, 40.

So forty people can fit on the benches.

Okay.

What about this one now? How many people can fit on these benches? How could we write it as an equation? Hmm, Well I know that I've got ten people can fit on each bench so we can count these in ten.

10, 20, 30.

So thirty people can fit on these benches.

10, 20, 30, 40.

So forty people can sit on these benches.

So I've got thirty add forty, and I would write that as this equation, 30 add 40 is equal to.

So I need to add these two digit numbers together.

I could do it, by counting all of my benches in tens, but I'm going to show you how we can use our number facts to add these tens together.

So if I know, that three ones, add four ones is seven ones.

Then I also know, that three tens add four tens is seven tens.

We know that three tens is 30 and four tens is 40.

So this is essentially our equation up here.

Three tens add four tens is seven tens.

Seven tens is seventy.

Let just count, let's double check.

10, 20, 30, 40, 50, 60, 70.

So the answer to my equation is seventy.

Let's have a look at this next one.

How many people can fit on these benches altogether? How could we write this as an equation? Well, I've got 10 people can sit on each bench.

So I've got 10, 20 people can fit on these two benches and 10, 20, 30, 40 people can fit on these benches.

And I need to add them together because I want to know how many people can fit on these benches all together.

So my equation would look like this, twenty add forty is equal to? Let's use our number facts to help us work this one out.

To help us work out how many people can fit on the benches altogether.

If I know that two ones add four ones is six ones, then I also know that two tens, which is 20, add four tens, which is 40, is equal to six tens.

Six tens has the value of sixty.

10, 20, 30, 40, 50, 60.

So the answer to my equation is sixty.

Okay.

It is time for your talk task now guys.

So using these equations where you've got multiples of 10 and you're adding them together, I want you to derive the number facts that can help you to answer these questions.

You're going to use the sentences below to help you.

So if I know mm ones, plus mm ones is equal to mm ones, then I know mm tens plus mm tens is equal to mm tens.

Let's do the first one together and then you can have a go at the rest.

I'm going to start with this one here.

So, if I know, that three ones plus four ones is equal to seven ones, so three add four equals seven.

Then I know that three tens, which is worth 30, add four tens, which is worth 40, is equal to seven tens, which is worth 70.

So I know that thirty add forty is equal to seventy.

Like this, pause the video now to have a go at the rest of these equations and play the video when you're ready to continue.

Okay, team, we are going to have a go now, at subtracting multiples of tens in this half of the lesson.

So let's have a look at our, so let's have a look at our question.

At the top of the page, eight benches were full at lunch, then everyone from three of the benches left, how many people were still on the benches? So we know that 10 people can sit on each bench.

So we have eight benches that are full at lunch.

Then everyone from three benches, so all 10 people in this bench, all 10 people on this bench and all 10 people on this bench leave.

And we want to know what's left over.

We're going to use our number facts to help us work this out.

And we're going to use our deeds as well.

So if I know that eight ones, take away three ones is equal to five ones.

Then I know that eight tens, over here take away three tens is equal to five tens Like this.

Let's have a look at that in terms of equations.

So if I know that eight take away three, so eight benches, take away three is equal to five.

I know that 80 take away 30 is equal to 50, so we know that there were 80 people at the beginning in this in this picnic bench area, 30 left because everyone from three benches left which means that there are 50 people left on the benches.

Let's have a read of this next one then.

So we have nine benches were full at lunch, then people left from five of the benches.

How many people were still on the benches? Okay, so let's use our deeds and our number facts to help us.

I know, that if I have nine ones, take away five ones I'm left with four one's.

Therefore i know that if I have nine tens take away five tens, I'm left with four tens.

Let's have a look at that as an equation.

If I know that nine take away five is equal to four.

In other words, nine benches take away five benches is equal to four.

Then I know that 90 take away 50 is equal to 40.

So there were 90 people at the start of lunch because all of the benches were full, then 50 people left, So 40 people were still left on the benches.

Okay, it is time for your main task now guys.

So I'm just going to go through an example for you and then you are going to have a go at one yourself.

So, we're going to use a number of facts today and also drawing out deeds to help us exemplify our number facts.

So my equation is two add three.

If this was an a part-whole model, I know that my first part is two, so I'm going to draw that in there.

My second part is three.

So I'm going to draw those in there.

And I know that two add three gives me one, two three four, five.

So five is my whole.

So two add three equals five, because I know, two or three equals five that is going to help me know 20 add 30.

One of my parts is 20.

So I'm going to draw those two tens, one of my parts is thirty, so I'm going to draw three tens to represent 30.

So I have five tens all together, which is 50.

So 20 add 30 is 50.

If I know two add five equals five, then I know 20 add 30 equals 50.

You are going to have a go at this yourself now guys, so pause the video now to complete your task and resume the video once you're finished and are ready to go through the answers.

Brilliant, let's go through them.

So these are the answers to questions one and two.

So if I know that four, add three is seven, that I know that forty add 30 is 70.

If I know that eight is equal to five, add three and five add three equals eight, then I know that eighty is equal to fifty add thirty.

Let's look at questions three and four now, if I know that seven take away two is five, then I know that 70 take away 20 is 50.

If I know that nine take away something is six or nine take away three is six, that I know that nine take away 30 is equal to 60.

Last question, then, if I know well, I know my whole is six, which is equal to something take away two, another eight to take away two is six.

Lets look at our last question then, My whole is six, So my whole is six and I'm looking for something take way two is equal to six.

I know that if my whole is six, then my, if my hole is six, then this part must be eight.

Oh, let's just change that, it should be eight because eight take away two, is equal to six, which tells me, that 60 is equal to eighty take away twenty.

Well done on getting through those team, great work today.

Team, that concludes our lesson for today.

Well done on all of your hard work with adding and subtracting multiples of ten and I look forward to seeing you very soon on another session.

Bye bye.

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

All that's left to do now guys is complete your quiz.

So good luck.