Lesson video

Hello mathematicians, Ms. Charlton here, and Hedwig, back with some more maths learning.

Hope everybody is feeling well and ready for some more math today.

Now, before we get started, one of my peoples came into school, and they told me a funny joke, and I thought I would share it with you.

It goes like this, what did the baby octopus say to the mommy octopus? I want to hold your hand, and hand, and hand, and hand, and hand, and hand, and hand and hand.

I thought that was a bit silly, but very funny.

Hopefully that made you chuckle.

Let's find out what we're going to do today.

So we are going to be adding a one digit number to a teens number, using a known fact.

We're going to learn how to use number bonds when adding teens numbers, and then we're going to identify and solve equations using number bonds.

Then you'll do your independent task and an end of lesson quiz.

Today you're going to need a pencil and some paper.

Let's warm ourselves up with a brain teaser, we want to skip count in twos, starting from zero.

So if we start at zero, and we go up, we increase by two, we would jump from zero to two, two, four, can you complete the rest? Say it to your tool partner, ready? Two.

Should we check together? Are you ready? Zero, two, four, six, eight, 10, 12, 14, 16, 18, 20! That was skip counting in twos, we increase by two each time, well done! Let's go again with our star words, get your hands ready, hands up, star words! Number bond, known fact! Now known fact is something that you already know, which is going to help us with some even trickier maths today.

Look at that picture, can we see all of those presents, and those little elves running around, sorting all those presents out? What do you think you'd like? Oh, I can see a candy cane, I quite like a candy cane, or maybe a football, or maybe a book? Oh, I can see a trumpet! What can you see? Tell your two up partner which of those presents would you want most of all? I think Hedwig would want the trumpet as well, I think she likes to make quite a lot of noise, especially when she's squawking.

Now I want to know, how would we count all of those presents? Because there are a lot, aren't there? Absolutely loads of presents.

Now what we have been doing is using a number line, so we can count them all by jumping along on the number line.

But the problem is that the more counts and the more jumps that you do, the easier it is to make mistakes, and we need to learn some strategies to help us to count really accurately and really quickly.

So that's what we're going to start practising today.

The easiest way to do this is to make groups of 10.

So first of all, I can see the elves wrapped 14 presents, can you see, there's 14 presents there, and then they wrapped five more presents.

14 plus five, how many presents have they wrapped altogether? Again, it's tricky to do that, isn't it? We'd have to count all the way along the number line, which means that we might make a mistake.

But if we do this, making a group of 10, it makes it much easier for us to see what the equation might be that we need to do.

So I've got a group of 10, and four more, there's the 14, 10, 11, 12, 13, 14.

14 presents, plus five more presents.

14 plus five.

Now what we can do is use what we already know, use our known facts, ooh, that's our star words, use our known facts to add the numbers together, like this.

10, four, there's our four ones, plus five.

I know that four plus five is nine, which means that 14 plus 5 must be a very similar equation.

Hmm, four plus five, and 14 plus five.

Let's have a look at that with cubes.

Can you see the stack of cubes at the start? I've got four plus five, four cubes plus five cubes, which is the same as saying 14 plus five.

What's the same and what's different about those two cube representations? Hmm, well I can see that I've got four cubes there, and I've got four blue cubes in the other equation, and I've got five yellow cubes and five yellow cubes in the other equation, the only thing that's different is the stack of 10 cubes, because 14 has got one ten and four ones, but four has just got four ones.

Four plus five, 14 plus five.

Now 14 plus five is tricky to work out, but if I can work out four plus five, which is equal to nine, then I know that 14 plus five is equal to 19.

Four plus five is equal to nine, can you say that? 14 plus five is equal to 19.

Well done everybody! Let's count out again with this one, using what we know, using our known facts, our known bond, to help us solve the equations.

We've got another tree with acorns on here, and we're adding more acorns to it.

So we've got our first, then and now story, let's see what we're going to do with it.

First we need to make a group of 10, so you count the acorns currently on the tree, and I can see that I've got 11 acorns, 10, 11, plus one two three four five six seven eight.

11 plus eight, hmm, 11 plus eight, that's a bit of a tricky equation to do, but what could I do to help me? Ah, I could use my known facts, 11 plus eight, I could find a number bond, I know that one plus eight, plus my one acorn, plus eight acorns, is equal to nine, so I know that one plus eight is equal to nine, which means that 11 plus eight is equal to 19.

The only difference there is that 11 has got a 10 in it.

One plus eight is equal to nine, so 11 plus eight is equal to 19.

It's a little bit tricky, that, isn't it? Let have another go.

Oh, I've got the eggs.

First of all, I need to find a group of 10.

So I can look at all of my eggs, and I can group them and see how many ones there are.

I've got a group of 10, and then one two three four five six, six eggs, 10 and six, so there are 16 eggs, plus how many? Plus three, 16 plus three, oh, 16 plus three, that's a teens number, so it's a bit tricky to add, but what could I do to help me? I could use a known fact, well done, what could I use? Known facts, let's see what know fact we could use.

If I know that six plus three is equal to nine, there's my six eggs, plus three eggs, then I know that 16 plus three is equal to 19.

Six plus three is equal to nine, 16 plus three is equal to 19, can you say that? Six plus three is equal to nine, 16 plus three is equal to 19.

Really great mathematical thinking everybody.

Now, your independent task, you don't need to solve all of the equations, I just want to know which one would help you solve it? If you want to work out the answer at the end there's a box for you as well, but I just want to know which of these number bonds would help you solve those equations.

For example, 12 plus seven, hmm, 12 plus seven, which number bond, which known fact in that box would help you solve that equation? 13 plus six, oh, that's tricky, that's a teens number, but which number bond will help you solve it? And then 15 plus four, which number bond, which known fact would help you solve that one? Have a go at matching those up, and then come back and we'll check the answers together.

Let's have a look, what did you find out? 12 plus seven, oh, that's a tricky one, it's a teens number, but if you can see that 12 plus seven, that's the same, if I say seven plus two is equal to nine, then 12 plus seven is equal to 19.

There we go.

13 plus six, oh, that's tricky, but I know that three plus six, or six plus three, then I know that 13 plus six is equal to 19.

Six plus three is equal to nine, 13 plus six is equal to 19.

And the last one, 15 plus four, oh, that's a tricky one, that's a teens number, but if you look at the ones, five plus four.

Five plus four is equal to nine, 15 plus four is equal to nine.

You did a really great job with that, that was tricky everybody, should we wake up Hedwig and tell her what we did? Wakey wakey Hedwig, wakey wakey.

Right, what did we do today? Well, we were adding teens numbers together, and we needed to solve some equations, but some of them were a bit tricky.

So what we did was we used known facts to help us, do you understand? Ooh, Hedwig's not sure today, Hedwig, you're so brave to tell us that you're not sure about the learning today.

Should we think of another way to explain it to her? Right, it was tricky, wasn't it? So because sometimes adding together is tricky, especially when we get to teens numbers, we used a different strategy to help us add that number.

We would often count on a number line and add them up, but in those cases we could often make a lot of mistakes.

So what we did this time was to use what we already know, for example, 16 plus three, that's tricky.

16 plus three, but if I do six plus three, that's equal to nine, so 16 plus three must be equal to 19, because the only difference is that 16 has a 10.

Is that easier to understand now, Hedwig? I think she's a bit happier now.

It's okay sometimes if you don't understand it, we can just explain it, and it's really brave to say when you find it tricky.

Have a little go at your quiz now, and I'll see you all again very soon, buh bye!.