Adding two

Key Stage 1

Maths

Addition and Subtraction

﻿Hi, everyone. It's Mrs. Par back with you again. So as we always do our first job is to go over the practise activity from the last session. You looked at consecutive numbers and where we have consecutive numbers in a subtraction the difference is one. Do you remember that? Well done. Okay, so you were using that to help you sort out these expressions into a table where they were either had a difference of one or not a difference of one. Should we see how you got on? Okay, so the first one we're looking at here is four minus three, four minus three. What do you notice about those two numbers four and three? They're consecutive. So they have a difference of one. Well done. So what about the next one? Eight take away seven. Are they consecutive numbers? Yes, they are, aren't they? So they have a difference of one. Now I wonder if you got caught out on this next one. One takeaway zero. Are one and zero consecutive numbers? Yes, well done, they are. They're next to each other on the number line, aren't they? Well done. So they do have a difference of one. One takeaway zero is equal to one. Good, let's have a look at the next one then. Four subtract one. Well, there's a one in there, isn't there? But are they consecutive numbers? No, so do they have a difference of one? No, they don't. Well done everyone. Six take away four. Six minus four. Not a difference of one is it? Because they're not consecutive numbers. Well done. Now nine subtract seven. Not consecutive numbers. Not a difference of one. Well done. Now here's some really big numbers, but did you spot the pattern here as well? 39 minus 38. What do you think? Are they consecutive numbers? I wonder how you knew. They are aren't they? If we've got 39 and 38, they must be consecutive numbers because nine and eight are consecutive numbers. Well done. So they do have a difference of one. I bet you did all sorts of brilliant examples for yourself. And as long as the two numbers were consecutive they will have a difference of one. Well done. So we're going to start today's lesson by having a look at our number block friends. Can you wave hello to your number block friends? There they all are. All multicoloured. We're going to look at the shape of them first. Do you notice anything about the shape of our number block friends? Do some of them have a similar shape and other ones have a similar shape? Have a look and see. I wonder what you spotted with our number blocks. Is it easier to also look at them with the Numecon underneath? We can see the shapes even more clearly with the numbers in the Numecon and on our number line. So what have you spotted about the shapes? Some of the shapes have a smooth, even you might say, top to them, don't they? Can you see that two, four, six, eight, and 10 all have a nice, even smooth top to them. There are no sticky up bits, okay? So what does that mean? Let's have a think about what that might mean then. I bet you, I bet you're all shouting at the screen. They are all even numbers. Good job. They are our even numbers. So what do you think then about the shape where they're not smooth at the top? That one is, but it's all by itself. It doesn't have a partner. And the poor here. There's a poor one sticking up on his own and nothing next to him there. Poor number three. And then number five. We've got a little gap there, haven't we? His head sticks up all by himself. And the same with number seven and the same with number nine. What does that mean if they've got an odd little bit sticking up? Well done, they are our odd numbers. So now we're going to do some counting but we're going to do it in two different ways. First of all, we are going to say all the numbers in our number line, but we're going to whisper the odd ones and say the even ones much more clearly. Can you see which ones you can see more clearly on our number line? Good, you can see the even ones more clearly, can't you? Are you ready to count from zero? Zero, one, two, three, four, five, six, seven, eight, nine, 10. Well done. But this time we're not going to say our odd numbers at all. We're actually going to skip count up, aren't we? We're going to skip counting in twos starting at zero, ready? Zero, two, four, six, eight, 10. So we've said all our even numbers by skip counting in twos. Brilliant, well done. Now we're going to do exactly the same thing. We're going to count through, but we're going to whisper the even numbers, the ones that are faded out this time. So let's start on one. Are you ready? We're going to say the odd numbers. One, two, three, four, five, six, seven, eight, nine, 10. Good. Now let's go skip counting again, but starting on one this time. Can you do that? It's a little bit harder. Are you ready? One, three, five, seven nine. Should we go backwards as well? Let's really challenge ourselves. Let's go backwards, ready? Starting at nine. Nine, seven, five, three, one, well done. So this time we're going to make it a little bit harder. All our numbers are there, but we are going to skip count starting on zero, which means you can skip count in twos, which means we're going to say all the even numbers. Are you ready? Zero, two, four, six, eight, 10. Let's start at 10 and go back. 10, eight, six, four, two, zero. Well done. I hope you got on okay with that. Now I think this is a little bit harder cause we don't do this as often. We're going to skip counting twos, but starting on one. So we'll end up saying all the odd numbers. Good, are you ready? One, three, five, seven nine. Should we go back? Nine, seven, five, three one. Good job everyone. Now we've got a little bit of a missing number problem. We've got the number seven here in the middle and over here in this missing number box we need to put the next odd number. Okay, there's an arrow going that way. So it's not the next number. It's the next odd number. And over here, we need the previous odd number. So again not the number before, but the previous odd number. So how are we going to work this out? What do you think? Here we've got seven. So the next number would be eight. Is that odd? It isn't, is it? So our next number will be nine, you're absolutely right. Well done. So in here I'm going to write the number nine. Well done. Okay, what about then this other number? We need to look at what our previous odd number is. So here we've got seven. What number comes before seven? Think about your number line. Six, but that's not odd is it, it's even. So now we need six. Five, well done, let's put it in then. Good job everyone. Shall we just use our number line to check? Here's our number seven and we said, didn't we? The eight there. but that's an even number because it's smooth at the top. Whereas nine has a bit sticking out. So it must be an odd number. So there we go. Well done. And the other way there's the number five, our previous odd number. This time we're looking for the next even number, we start with four. Is that an even number? Yes, it is. Well done. Can you picture in your head? The shape of a number four is usually a square, isn't it? Nice and even at the top. Good, okay. So we're going to look our next, even number. Is it the number next to four on the number line? No, well done. We have to jump over the number five to get to the number six, well done. Okay, and then the one before, the one that comes before four, not just the number before four, because that is three. But the number before that is two, well done. Let's double check again. Here's our number four, our next even number jumps past the five it's our number six. And our previous even number jumps past the three and is the number two. So what is it that we're actually doing when we skip counting in two or when we're saying all the even numbers? What calculation are we doing? Should we should, should we have a look? Okay, so when we go from zero to two, what's happening? Two to four, four to six, to eight, to 10, what are we doing? What are all those jumps? What calculation are we doing? Well done everyone. We're adding to each time, aren't we? That's what skip counting in twos does. We're adding two to the number we landed on. Well done. So now we're going to concentrate on that idea of adding two, okay? So we're going to start with zero. There's nothing in my tens frame, is there? And we're going to add two to that number. Are you ready to see what happens? Zero add two. Oooh, we've got the whole row on the bottom of our tens frame filled up. So zero add two is equal to two. Good, well done. So if we start with two and add two to it we get four, you're absolutely right. Four is our next even number. Okay, do you think that will always work? If we have an even number and we add two to it, do you think it will take us to our next even number? Should we try it out? Let's have a go. So this time we start with four and we add two. Oh, look, what have we got? It's like the counters just slotted in underneath, wasn't it? They've just gone in underneath and push the other ones up. It's still even at the top, isn't it? There are no one's popping up on their own. So we've got six, which is our next even number. Does look like it works, doesn't it? Okay, do you think you can think of a rule? We're going to start with this six this time. Are you ready? What do you think's going to happen? Can you predict what the answer's going to be? So we start with six and we add two. Is that what you thought would happen? We have got eight, six, add two is equal to eight. We're on our next even number. I bet you all know what's coming next. Ready to start with eight. Eight add two is equal to 10. You know that one, don't you because it's one of your special number bonds to 10. And we can see that our tens frame is full. Eight which is an even number add two is equal to 10, which is our next even number. So if this always happens, we can say it's a generalisation. We can know that it would always happen. Adding two to an even number gives the next even number. It's going to be important for us to remember that because it makes adding two really easy. So then what if we skip count starting on one, like we did earlier? Should we see what happens? So I've got the same skip counting one, three, five, seven, nine. I've jumped in twos still. So what calculation do you think I'm doing? Some of you have got it, haven't you? We're just starting two again. We just started on the number one instead of zero, okay? So we're jumping all the odd numbers. So I just want you to have a look now at what's happening here. We've just got one counter all by itself in our 10s frame. And we're going two add to this. Can you picture what might be about to happen? Have a think. Two counters have come to join it. So we had one and we've added two and we now have three counters, our next odd number. Okay, so we're starting with three this time. Let's see what's the same and what's the difference to when we were doing it with the even numbers. Are you ready? Three add two. Okay, so they just slotted in again, didn't they? So what's the same? Two more come and join the tens frame and push the other ones up. But what's different? It's not even on the top, is it? It stays odd because it just pushes them all up and we've still got this gap. So we've still got an odd number. Three plus two is equal to five, our next odd number. Well done everyone. So now we're starting with five and we're going to add two. Can you predict what it's going to be? Five add two is equal to seven. Well done. Our next odd number. I bet you all know what's coming next. Are you ready? Last one. We start with seven and we add two. Seven, an odd number, add two is equal to nine, our next odd number. I think this one works as well. So can we write another generalisation? Adding two to an odd number gives the next odd number. So here we have our two generalisation side by side and there are some bits that are the same and some bits that are different. So I'm going to read you the first one at the top. Adding two to an odd number gives the next odd number. Then the second one. Adding two to an even number gives the next even number. Why don't you pause here and just have a think about what is the same and what is different? Did you come back? Well done. So both times in both generalisations, we were adding two, weren't we? But on one we started on an odd number and it gives us the next odd number. And in the other generalisation we are still adding two, but we start on an even number and it gives us the next even number. There's just one more thing I wanted to tell you about adding two. And it's really important, but you already know it because we've already come across this idea and this generalisation, are you ready? So at the top here, I've got seven add two, we know it's going to be nine, don't we? Because it's an odd number, add two gives us the next odd number. But do you remember what we said before? Have a look at this generalisation. When you change the order of the addends the sum remains the same. So what's going to be down here under my box. What do you think I've done? We changed the order of the addends the sum remains the same. Tell me. Good. If seven add two is nine then two add seven is equal to nine. It doesn't matter where the two is. If there's a two in added on in your equation, then it's going to be the next odd number. I think, you know, what's coming now. I think you can already predict it. So here we've got the even version, haven't we? Six add two is equal to eight. And where do you change the order of the addends the sum remains the same. So what's under here? Two add six is equal to eight. And all we have to do is in our head, we just swap it around don't we? Because it's easier to say an even number add two is the next even number. So it's just easier to look at it as if six is at the front. So this is what we're going to have a go at now. Can you see all these sums down the side? We are going to have a look, first of all, at these ones here, these equations, okay? And you're going to have to fill in the missing number in the equation. So have a look, first of all, at that first number and then we are adding two to it and we're going to put the number in the box. Are you ready? Because what I would like to do is I'm going to say the first number then you're going to add two to it in your head. You're not going to count on, you're going to jump to the next odd number, aren't you? Because I hope we've spotted that all these ones at the beginning of odd. Are you ready? So I will say one, you add two to it in your head. Do that jump. Add two is equal to three, well done. You ready? I'm going to say the next one. Three where to, is equal to five. Good job, well done. Right next one. Five is equal to seven, our next odd number. Oh, it's time we're starting with seven. Seven add two equal to nine. And the last one on this list, we're starting with nine. Nine is equal to 11. Well done. We hadn't gone up that high, had we? Good job. What did you notice? Did you notice that these were all the odd numbers, we added to and it made the next odd number. Then what did we start with? We started with that odd number, didn't we? Good job everyone. Right, I want you to have a pause. And I want you to have a go at this second list here and then we will go through them again. Don't forget when we're adding two to an even number it gives us the next even number. Have a go. Ready everyone? Let's do them together then. Zero add two is equal to two. The next even number. Two add two is equal to four. Fantastic. Four, you add two is equal to six. Six add two is equal to eight. And eight add two is equal to 10. Great job everyone. Well done. So it's time for me to leave you with your practise activity for today, okay? And just like the page before you've got two lists of sums, okay? Two lists of equations with a number missing, the sum is missing. So these are the three things you're going to have to remember. Adding two to an odd number, gives you an odd number. Adding two to an even number gives you the next even number. But this is the one that I need you to remember because we haven't done this yet. This is the extra bit of challenge. Are you ready? When you change the order of the addends the sum remains the same. You're going to need all three of those rules to help you to solve these problems without having to count on on your fingers. You know, the rules. So it's time to use them. Okay, have fun everyone. Bye.

Adding two

Adding two

Lesson details

Key learning points

Licence

Video

Lesson appears in

UnitMaths / Addition and Subtraction

Maths