Let's see what you have learnt about adding and subtracting 1-digit numbers to and from 3-digit numbers today

Tick the 3-digit number below

Which one of these shows a number bond to 20

12 + 9 =

222 + 7 =

308 + 8 =

Adding and Subtracting 1-Digit Numbers to/from 3-Digit Numbers Quiz

﻿Hello everyone ,I'm Miss Brinkworth I'm going to go through this math lesson with you today. So if we just go back to having a look at our learning objectives we're adding multiples of 10 to three digit numbers. And what we're looking at is the mental strategies that we can use to do that really quickly and efficiently. So, If you look at our lesson agenda today what we're going to be doing is looking at a part/whole model and how that can make it clear what it is the question is asking us to do. We're then going to think about using your known facts. So if you know a lot of maths already that's going to really really help you with today's lesson. We're then going to have a really good look at regrouping because regroup, splitting numbers up and then regrouping them can be a really good way of making sure that our mental strategies are really accurate. And then you're going to have some independent work which will give you a chance to practise these new skills. And we'll finish with that exit quiz which allows you to see how well you've taken on today's learning. Okay, so for this lesson you are going to need something to write with and something to write on so please grab a pen or pencil and some paper. It would also be really useful if you could ask a parents to help you find some online deans. So deans are the little cubes that we use during lesson to help us when we're adding and subtracting. So if you could ask your parents or carer to help you find some online and how can you use them during this lesson, that would be really useful. Pause the video here and have a go. Well done. Hope you all managed to find what you need. Okay. Little warm up here for you then nice, simple, efficient questions and to just get you thinking about how we add numbers. So choose the two, a few of these to just add together, and when you do think about what strategies you've used so what steps have you taken in your mind to get you to the right answer. Pause the video and just answer a few of those. How did you do? I always think it's very interesting which question you went for first. Did you just start at the top and pick the first one, or did you have a look through and pick which one you thought was going to be quite easy? Pick, which numbers you like adding together. So maybe you really competent with adding six and three. So you went for sixty three add thirty. What I wanted you to do was think carefully about what it is you've actually done to get to the right answer. So let me explain what I mean by this. I picked fifty four add forty, and I got the answer in ninety four. But how did I get there? What did I actually need to do? What should I already need to know? Well, actually what I did without really thinking about it, was I partitioned those numbers into tens and ones, and then I added the tens separately to the ones. And what I did to do that was I saw that it's fifty add forty which five add four equals nine will help me. I know that five at four equals nine, so fifty at forty must equal ninety, and then there's just that four in the ones column to make sure that I move over as well. I wonder what strategies you used. I would be amazed if you didn't use a really similar strategy when you were doing those questions in your head. Okay, let's move on then, and think about what we're doing today. So this is a part/whole model, and you'll see this on some of the slides as we go through the lesson. What it is ,is it's a way of working out what we already know, and what we need to know. So in a part/whole model this question would be a hundred and, sorry, three hundred and forty two add twenty And what that's the information we've already got We know that what we're being asked is three hundred and forty two add twenty. The unknown, what we're looking for, what the answer will be is in that empty box. That's the whole. We've got the part , we want the whole. We've got the part, these two, two set, two parts and we will be looking for the whole, okay. So this is the sum that that part/whole model shows at the moment. Now remember with addition, that you can do addition sums in whichever order you like. So when we're talking about mental strategies, it's up to you to think about which you prefer. Have a look at those two sums there they will get exactly the same answer. But it might be that you prefer one over the other. I certainly prefer to have the big number first but it doesn't matter. So feel welcome throughout the lesson, if it's useful for you to swap those, the order round on these questions. Okay, so three hundred and forty two add twenty, how are we actually going to answer it today? Well, what we need to think about is the learning objective which is that we are adding multiples of ten. This means that we are focusing in on the tens column. So what the sum that we need to do really, is forty add twenty three hundred and forty two has forty in the tens column. And obviously we're adding twenty to that. So the sum we're doing is forty add twenty . The fact that we already know that we can use to help us with that is four, add two. Four add two is six Forty add twenty is sixty. So three hundred and forty two add twenty is three hundred and sixty two. It's just the tens column which has changed, and it's gone up by two because twenty has two in the tens column. And now we can see that's what we need to do for that question. And what we've done is we've done four add two or two add four, doesn't matter which order you do them in to give us six, which allows us to work out that its sixty in the tens column and there's that sum. And then we can complete our part/whole model because we've worked out what the whole is. We've taken the two parts, we've added them together and we've got the whole. Okay, here's another one. This time, we might want to have to think about using those online deans. If you haven't found any don't worry you can use mine, but if you have, try and use them now to just set out the question, two hundred and thirty four and there I started with my deans two hundred and thirty four added to forty. You don't need to answer the question, just pause the video and have a go at finding the right number of deans to answer that question. Right what will forty look like with our deans then, well we what you need, four lots of ten. There they are. So we've got two hundred and thirty four, add forty and let's have a look at what that looks like. We've added that forty into our tens column. So instead of four, lots of ten left we've got four add three. Four add three is seven. So we've got seven, lots of ten. We've got seventy. So our answer to that question is two hundred and seventy four. There we can see that it's the tens column, which has changed. Okay, here's your part/whole model. What's the answer to this question? We've got four hundred and thirty six add thirty Well, we're going to use that fact three add three six. Hopefully we'll know that one quite clearly, and thirty add thirty is sixty. So our tens column is going to change, and it's now going to be six. Really really well done. Okay it's our turn, pause the video and have a go at using that strategy. How did you get on? Well hopefully, you could see if you were stuck that what you needed to do was two add five or five add two which would then give you twenty add fifty. Two add five is seven, twenty add fifty is seventy, so there's our answer at seven hundred and seventy five. Really really well if you saw that. How is this question different then. How am I going to end up with a different type of answer with this question? Well, let's go back to having our deans. Now we only really need to have a look at our tens. So I'm just going to get the tens. I'm going to get eight tens there for eighty, which is in two hundred and eighty, eighty and I need to add to that, Twenty, eighty add twenty. Well I know that eight add two is ten, so eighty add twenty I make ten ten times bigger, gives me one hundred. And you know that with deans when we get to a hundred our block changes and it looks like this. This is because we've gone into the next place value column. So for this question, it's not just the tens column that's going to change, it's the hundreds column. So I've added together my tens and I've got one hundred. I just then need to add that together With the two hundred I started with in two hundred and eighty, to give me three hundred. Have a go here, if you're stuck, here's something to help you. Three add seven and thirty add seventy, have a go Okay, how did you get on? Got a little sneak peek there. Three add seven is ten, so thirty add seventy is a hundred. But be careful, because your final answer is six hundred and five. You can't ignore that there is still a five in the ones column, And so make sure you move that over along with the extra five hundred , so five hundred add the one hundred that you made by adding thirty and seventy and then the five's left over. Okay, one more type of question for us to have a look through together then. How is this one different again? Well, we're certainly going to bridge a hundred this time but we're actually going to go over the hundred. We're not just going to bridge up to a hundred, we're going to go over it. So how will we do it? We've got two hundred and eighty three add forty. I know this is going to need me to regroup because eight add four gives me a number bigger than ten, so how am I going to do it? Well, one of the things you can do is partition. Partition forty into twenty and twenty. Why twenty and twenty? Why not thirty and ten? Well twenty and twenty is a nice way to partition forty for this question because, when I add my first twenty, I go over into three hundred and three. Then adding my second twenty is really simple because I just need to amend my tens column. Gives me that answer three hundred and twenty three. Your turn, for some help here if you're stuck, what I would, I would recommend if you're stuck is splitting that thirty into ten and twenty. First add the ten, then at the twenty. See how you get on. Right? Well, if you followed my advice and you added ten first, a hundred and ninety five add ten is two hundred and five, You've then got twenty more to add, to give you two hundred and twenty five. A little bit more practise for you here then. Look at each question carefully and think about which strategy you need before answering them. Really well done everybody. Here are the answers, I'm not going to go through them in too much detail but really well done if you tackle question four which requires that be grouping over the hundreds. Really good. Okay, it's time for your independent work now. So pause the video and take as long as you need, we'll come back together and go through the answers. Well done everybody. Let's have a look at the answers together. Please don't worry if you get some wrong, this is new learning. But to have to think about any incorrect answers, and maybe what mistake you made. It says here to pick a three digit number and one of those multiples of ten and just practise adding them together. I can't go through all those answers with you cause I don't know which ones you picked. But you can practise making You can get into the habit of just having another look at each question and deciding whether you've got it right. So certainly ,your three digit number should be bigger than the one you started with. And you can just make sure that you, it looks reasonable that it's got bigger and it looks reasonable with the amount that you were adding to it. Hopefully a lot of you got onto that challenge question as well where you had a go at making these, these amounts. Now I'm going to give you some answers. I don't know if these are the only answers, but these are the ones I came up with. So if you had to go at making six hundred and eight, you could do it like this. Five hundred and seventy eight add thirty. You can make four hundred and twenty five with three hundred and forty five add eighty, and for two hundred and twenty nine you could do a hundred and ninety nine add thirty. Really well done if you challenged yourself and got on to those questions. Okay, finally then, this statement is it sometimes always or never true, when you add a multiple of ten to a three digit number, only the tens digit changes. Well, hopefully you've able to see throughout this lesson that that is sometimes true. Sometimes only the tens digit changes on a question like this, a hundred and two add thirty gives us a hundred and thirty two. Only the tens column has changed there. But that's not always true, because for a question like this, the hundreds column will change as well when we have to regroup. Okay, what real life problem might be being shown here in this bar model? Well, you can just come up with anything really. I came up with two schools visit the zoo on the same day, Three hundred and fifty seven from school A and seventy from school B. How many is this altogether? I would expect to see an altogether in your question. Okay, time for that knowledge quiz to see how well today's learning's gone in, but really well done on a lot of tricky new strategies today.

Let's see what you have learnt about adding multiples of 10 to 3-digit numbers

Which one of these is a 3 digit number?

674 + 20 =

654 + 30 = 694 True or false?

520 + 80 =

666 + 50 =

Adding Multiples of 10 to 3-Digit Numbers Quiz

In this lesson, we will use known number facts in order to mentally add multiples of 10 to 3-digit numbers. We will look at partitioning strategies and analyse place value to make mental addition more efficient.

Maths

Y3 Maths

Key Stage 2

Year 3

Adding multiples of 10 to 3-digit numbers

Addition and subtraction

Number

THEME

UNIT

Adding and subtracting 1-digit numbers to/from 3-digit numbers

Subtracting multiples of 10 from 3-digit numbers

Adding and subtracting multiples of 100 to/from 3-digit numbers

Adding two 3-digit numbers (without regrouping)

Subtracting two 3-digit numbers (without regrouping)

Applying rounding for estimating (adding)

Applying rounding for estimating (subtracting)

Adding two 3-digit numbers (regrouping in one column)

Adding two 3-digit numbers (regrouping in multiple columns)

Subtracting 3-digit numbers (regrouping tens to ones)

Subtracting 3-digit numbers (regrouping hundreds to tens)

Subtracting 3-digit numbers (regrouping in multiple columns)

Solving addition and subtraction word problems

Solving word problems with unknown values

Tia is looking after the neighbour's dogs. The adult dog eats 450 g more than the puppy. If the adult dog eats 875 g how much will the puppy eat?                            Does this question need addition or subtraction to answer it?

Which question would this bar model help to answer?

Before the final rounds of races on sports day, the green team had 372 points. They ended up winning the competition with 518 points altogether. How many more points did they make in the final round?

456 - 111 =

835 - 324 =

Does this look like a good estimate? 720 - 30 = 500

Edinburgh castle sold 345 tickets for tours on Monday. On Tuesday it sold 109 less. How many tickets were sold on Tuesday?

What is 27 rounded to the nearest 10?

Lesson overview:Adding multiples of 10 to 3-digit numbers

Core Content

Addition and subtraction: