Lesson video

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Hello Year 2, and welcome to our new unit called Exploring Calculation Strategies.

Today, we're going to be solving addition equations.

If you haven't already, please, can you now get yourselves a pencil and some paper? Pause the video now to go and get these things, if you haven't got them already.

I thought I'd start today by giving you a bit of an introduction to my cat.

She's called Nala and there's a couple of pictures of her on this slide here.

She's now six years old and she is definitely the boss out of her and Arlo in our house.

She rules the roost.

Okay, our agenda for the lesson today, we are going to be learning how to solve addition equations, then we're going to look at today's star words, we're going to be looking at different strategies you can use to solve addition equations.

Then there'll be a talk task.

We're going to look at how we can answer the addition equations.

Then there'll be an independent task and we'll review our answers together.

And then, there'll be a final quiz to find out what you've remembered.

Okay then, let's get started with today's star words.

So, I'm going to do my 10 yard turn, I'll read them out and then I'd like you to repeat after me.

Make 10, number bonds, partition, known facts, round and adjust, equation, near doubles.

So, our new learning today.

We've got an example on the screen here of an addition equation.

We've got 26 plus 30.

What I want you to do is have a think, how can we solve this equation? And what strategies do we already know that will help us to solve it? Have a little think.

I don't want you to have a go at solving the equation just yet.

Okay, we're going to have a look now at the strategies that we can use to help us solve this equation.

So, we could use known facts.

So if I look at my equation, I've got 26 plus 30.

If I know that two plus three equals five, then I know that 20 plus 30 equals 50.

So that will definitely help me.

I could partition one of the numbers.

So I could partition 26 into 20 and six.

I could partition both numbers.

But in this case we don't need to, because 30 is a multiple of 10.

So we don't really need to partition that.

We could count on in our tens.

So we could start at 26 and count on in our tens three times, because I know that 30 is the same as saying three tens.

These are the different strategies that could help me to solve this equation.

Next thing we're going to do then, is we're going to think about what resources or representations we could use to help us solve this as well.

So let's have a think.

We've got our 26 plus 30, and we've got three different representations on the screen below that we can use, sorry, to help us solve this equation.

So here I've got my dienes.

I can see here that there's one, two tens, so 20, and one, two, three, four, five, six ones, so 26.

I can see here that there are three tens, one, two, three, the same as saying 30.

So I can show, I can see sorry, that my dienes show that equation.

I've got at the button, a bead strength, or you could have a number line if you've got one at home.

Here, I know that I've counted up to 10, 20, one, two three, four, five, six, and I can mark on 26.

I can use that then to help me add on the 30.

And here, I've got my part-whole model.

I know that I've got 26, I want to add 30 to it to find out what my whole is.

The whole at the moment is the thing that I don't know, it's my unknown.

So, let's have a look then at how we do it.

I've chosen to count up in my tens, because I think that's the most appropriate strategy.

So we're going to put 26 in our heads and we're going to count up in our tens three times, because we've got the number 30, and I know there are three tens in 30.

So I'd like your home to join him with me, 26 in your head, we're going to count up in our tens three times.

36, 46, 56.

We should have all got to 56.

Now let's double-check using my dienes to see if I've got to the right answer.

So I have my 26, I wanted to add on my 30, there's nothing in my ones column here, because in 30, there are zero ones.

I've got six in my ones column and five in my tens column, which gives me 56.

Well done for those of you at home who are counting along with me.

We're going to have a look at another example now, Example 2.

46 plus 29.

I want you to have a little think about which strategies you think we could use before we have a go at looking at them together.

Give yourself five seconds thinking time to think about what strategy you might want to use.

Okay, then let's have a look through the different strategies together.

So again, I could use my known facts.

If I know that four plus two equal six.

So if I look at my tens, four and two, then I would know that 40 plus 20 would equal 60.

I could partition one number.

So I could partition 46 into 40 and six.

I could partition both numbers.

So I've partitioned 46, sorry, into 40 and six.

I could then partition 29 into 20 and nine.

Or I could use a different method called round and adjust, it was one of our star words from earlier.

29, if I look at it really carefully, is quite close to 30, it's only one away.

So I could count in my tens and then take one back off, 'cause I've added one too many on.

So these are the different strategies I could use for this equation.

Let's have a look then, at what representations I could use.

I want you to have five seconds thinking time about the different representations we could use to help us solve this equation.

Okay, let's have a look at the different representations together then.

So, I've got dienes, I've got my part-whole model and I've got number lines or a bead string that I could use.

So here we've got our dienes to help us.

We've got 46 plus 29, let's double-check them.

So, we've got our tens.

One, two, three, four tens, that's correct.

And one, two, three, four, five, six ones that shows 46.

29, I've got one, two tens, and I've got one, two, three, four, five, six, seven, eight, nine, so I've got 29 here.

So that is showing me 29.

I've also got my part-whole model.

I know that 46 is one part, 29 is another part, and the unknown, the thing that I don't know at the moment is my whole, that's what I'm trying to work out now.

And then, I could also use my number line again, or my bead string.

So it shows 10, 20, 30, 40, 41, 42, 43, 44, 45, 46.

So I've marked it on.

And I could use that to help me jump up and add on 29 to get to my answer.

Now, I've chosen to use the round and adjust method.

Now I've chosen this, because I know that 29 is close to 30.

So I'm going to count up in my tens three times and then adjust my answer because I added on one too many, by taking one away.

So, let's have a go.

We're going to put 46 in our heads and we're going to count up three times.

46 in our heads, 56, 66, 76.

Now I know I've counted on one too many ones.

I'm on 76.

I have to take away one one, because I added a one to make 30.

So, 76 take away one would give me 75.

Let's double-check it using our dienes.

So, we've got our 46 here.

We've got our 29 here.

I've added on my ones here.

I've got one 10 and five ones remaining.

I've added on my tens here, I've got six tens.

I know that six tens plus one 10 gives me seven tens and I've got five ones, 75, the same answer that we just worked out together.

It's going to now be time for you to complete your talk task.

For your talk test today, you have got two different equations in the middle of your page.

Which strategy would you use? Don't forget to use the say out loud to help you.

I will use, strategy to add, I can partition, into, and, I have chosen this strategy because.

And don't forget your challenge today is can you explain why you would use your chosen strategy? Pause the screen now to have a go at your talk task.

We're going to look at our develop learning next.

So, I want you to have a look at the equation on the screen.

What do you notice is the same or different to the equations that we've just been looking at? Well done to those of you who said, "There's a box.

It looks like it could be a missing number." And that equal to sign is the other side of the equation to the equations you were just looking at.

So, I know I need to find the missing number.

I need to know which part of the equation I'm looking at.

So, I've chosen to use a part-whole model to help me here.

What do you think is going to be behind these two pink boxes? Have a little bit of thinking time, which numbers? Well done to those of you who guessed 38 and 40, because those are my two parts.

I don't know my whole at the moment.

So I need to have a think about which strategy we could use.

I'd like you now to have a think, what strategy would you use and why? Give yourself three seconds thinking time.

Okay, I've chosen to use the strategy near doubles because if I look at these two numbers, 38 and 40, 38 is very close to 40.

So I'm going to use 40 add 40, which would give me 80.

But because I added two on to my 38 to get me to the 40, I need to take two way, so it would give me 78 as my answer.

Your independent task today, you have got two slides today with some questions on them.

What I would like you to do is have a go at answering the question, the equations by solving them.

But I also want you to tell me how you solve them.

Remember, you can use dienes, drawing of dienes or number lines to help you.

You've got four questions and a short challenge.

Pause the screen now to have a go at your task and then we'll go through your answers together afterwards.

Welcome back Year 2.

Right, we're going to go through the answers together now.

So, Question 1: 54 plus 29.

I've got the answer 83.

I'm going to explain to you how I got the answer.

I chose to use the strategy round and adjust to make 29 into 30.

Then, I counted up in my tens three times from 54 to get me to 84.

Next, I took away one, because I added it on when I rounded, so I've readjusted it to give me 83.

Next question then.

78 plus nine equals 87.

This time I used the round and adjust to make nine 10, then I counted up in my tens once from 78 to get me to 88.

Next, I took away one, because I'd added it on when I rounded, so I had to adjust it to give me 87.

Question 3: The answer was 98.

I solved the equation by using near doubles.

I looked at my number, my number, sorry.

I could see 48 and 50 were close together.

I knew that 48 was close to 50.

So I did doubled 50 to give me 100, and then I had to take two away, because I'd added two on to give me 98.

Question 4: Seven plus eight plus three is equal to 18.

This time I used a different strategy, I used my number bonds.

I could see here, seven and three made 10.

So I used it to make 10 and used my seven and my three.

Then it was really straightforward, because I could just add eight onto 10 to give me 18.

My challenge to you today, let's have a look at what the answers could have been.

We were originally given an equation where we could see our two tens, our tens here, sorry, it was a two, and our 10 here was a two.

And our answer here was 52.

So I knew that two tens, so 20 add 20, would give me 40.

And I knew the difference between 40 and 52 was 12.

So I knew my two ones had to create 12.

So I chose to use six and six because I know that six add six equals 12, so my equation is correct here.

You could use other numbers in that equation.

Well done for everyone's hard work today.

I'm really impressed.

Pause now, to go to your final quiz and answer a few questions.

Thank you very much today and see you again soon, bye!.