Intro Quiz: Finding 10, 100 or 1000 less than a given number

Video: Finding 10, 100 or 1000 less than a given number

﻿Hi everybody, I'm Mrs. Crane, and welcome to today's lesson. In today's lesson, we're going to be finding 10, 100 or 1000 less than any given number. In a moment, I'll go through all the equipment that we'll need, so don't worry just yet. How are you today? I hope you're well, and I hope you've got, your math brain switched on. If you can, can you please turn off any notifications on your phone so you're not running to get distracted. Then if possible, find somewhere in your home that's nice and quiet and distraction-free ready for today's math lesson. When you're ready, let's begin. Okay, then let's go through today's agenda. So firstly, we'll be using some deines, then we're going to be playing a dice game, Then we're going to start looking at some number lines together, and finally it will be time for your independent tasks, which will be, can you find 10, 100 or 1000 less than any given number. And we'll go through the answers together. So, if you haven't already for today's lesson, you will need a pencil, some paper, and, if you've got one, a dice, if you don't have one, you can always ask a parent or a carer, if they could find an interactive version online for you. Please pause the video now to go and get these things, if you haven't got them already. Welcome back, so, as I said, we're going to be finding 10, 100 or 1000 less than a given number. So we're going to start off with the number 7,824. I've made it using my dienes, you can see here I've got 7,000, one, two, three, four, five, six, seven. I've got eight hundreds, one, two, three, four, five, six, seven, eight. I've got two tens and I've got four ones. I've also written it in numbers, and this place value we've got here. First thing I'm going to do, I'm going to subtract 10 from that. I'm going to take 10 away from that number. So you can see I've removed one of my tens deines, what number has it left me with? Well done. It has left me with 7,814. I only have one 10 here now, not two tens. So I'm going to put my new number into my answer box. Now, before I go on to subtract 100, I must go back to my original number. Why is it important that I go back to my original number? Well done, if I take 100 away from 7,814, I'm going to be left with the wrong answer. So let's make my answer, my number sorry, the original number,that is back to 7,824. Now this time I'm going to take away 100. Let's see what happens. How many hundreds have I been left with? Well done those of you that said you've been left with seven hundreds Mrs. Crane. So my new number is 7,724. And I can put that into my answer box here. What must I do before I answer my final question? Well done, I must go back to my original number, here it is 7,824. You can see, I made it back to 7,824. Now, this time I'm taking away 1000. So let's see what happens. I've taken away 1000, how many thousands have I been left with, I've been left with 6,824. So my new answer can go on this box here. Now I've got an always sometimes or never for us to think about today. So let's see when I subtract 10, it is the only digit in the tens column that changes, okay? What if I subtract 100? Its only the digit in the hundreds column that changes. When I subtract 1000, it is only the digit in the thousands column that changes, right? Let's have a look at an example to see if we can use that, to help us decide whether these statements are always sometimes or never true, okay? So my number is 4,005. The first thing I'm going to do is subtract 10 from it. Oh, what have you noticed about my tens column? Are there any tens to take away? No, there aren't, so I'm going to look at my next column. Are there any hundreds that I can regroup from? No there aren't, but there are four thousands. So I'm going to regroup one of my thousands to leave me with 3000 and to give me 10 hundreds. Now I still want to take away 10, can I do that just yet? I can't, I need to regroup one of my hundreds to give me 10 tens. I know there are 10 tens of 100 so then I can take away one of them. So I'm going to regroup, one of my hundreds. It's going to become 10 tens now can I take away 10. Yes, I can, so I'm going to take away my ten and let's have a look at what that new number is going to be. I now have 3000, one, two, three, four, five, six, seven, eight, 900, one, two, three, four, five, six, seven, eight, 95. So I'm going to put that new number in here. So it's 3,995, then my answer I can go in here. Let's think then, when I subtract 10 it's only the digit in the tens column that changes. So, let's have a look at my original number here. How many digits have changed between my original number and the number that I created when I subtracted 10? Well done, the thousands has changed. The hundreds has changed and so have the tens changed. So it's my statement always sometimes or never true, but it's not always true because in the first example we looked at, it was only the digit in the tens column. It must sometimes be true because we found an example where it is true. So it's definitely not never true, so our answer for this one is sometimes. Let's have a look then at what happens when we go back to our original number, we want to subtract 100. So here we are back our original number again, the number was 4,005. This time I'm taking away 100. Oh no, have I got a hundred that I can take away from straightaway? I don't, what do I need to do? Well done those of you that said, "Mrs. Crane, you need to regroup." So I'm going to regroup 1000, leaving me with 3000, for 10 hundreds. Can I now take away one of my hundreds? Yes I can, so I'm going to remove one of those hundreds. Now, what new number have I created? I've created 3000, one, two, three, four, five, six, seven eight, nine, 905. So my paste by the column here, I need to write 3,900 zero goes, there's a place value to show that, there aren't any tens and five ones. Let's put my new number in my answer column. Let's think back to this question then, When I subtract 100, it's only the digit in the hundreds column that changes. That's something that care, here's my original number. Here's my answer when I subtracted 100, how many digits and which columns have changed? Well done, the digit in my hundreds columns changed. And so is the digit in my thousands column. It's not always true because in that first example, we looked at together, we didn't have to do any regrouping with my thousands column, but it is sometimes true because in this example, we did need to regroup. It's definitely not never true. Finally, then we're going to look at 4,005 subtract 1000. And considering our last question. I want to take away 1000, I'm left with 3005, so I can change that here, at the place value grid. When I subtracted that 1000, only the digit and the thousands column changed, let's check. It was 4,005, it is 3005. Definitely only the digit in the thousands column changed does that mean that always, that's always the case of a thing. Can you think of any numbers, that might not be the case? What about if I was looking at a five digit number, I was looking at 10,000, I wanted to take away 1000. We're not going to look at those digits today. But if I was, I was looking at 10,005, I'm going to take away 1000, I'd be left with 9,005, which would mean my ten thousands column and my thousands column would change. So there are some examples that sometimes this isn't true. So it's not never again, it's sometimes we're not going to look at too many of those examples today. In fact, we're not going to look at any of those examples today, right? Then now it's time for let's explore and we are going to play a dice game. So what I'm going to do first is I'm going to explain how we do it. Then you're going to have a go, see if you can beat me. So, we're going to start with a number 1000. That definitely doesn't say 1000, does it? That number says 5,000, well done everybody. Can you beat me to make the lowest number possible? So, we roll at one we have to subtract 10. We roll at two, we have to subtract 100. We roll at three, we have to subtract 1000. We roll at four, we have to subtract 10. We've roll at five, we have to subtract 100. And if we roll at six, we have to subtract 1000. We have five rolls, so I'm going to show you first, then you're going to play against me. I roll my dice, I've rolled a one. So, I've subtracted 10 to give me 4,990. I've rolled to five, so I've subtracted 100 to give me 4,890. I've rolled a two, so I've subtracted 100 to give me 4,790. I've rolled a one, so I'm subtracting 10 to give me 4,780. And lastly I've rolled a six to give me 3,780. This is the lowest number that I've made. I get five rolls of my dice. So, what we're going to do now is we're going to play again this time, you're going to pause your screen. You're going to roll five times. Each time, you're going to take off the number that you roll from the grid above and see if you can beat me. I will go through my five rolls after you've had your go, okay? Remember, you're trying to get the lowest number possible. Pause the screen to have a go at today's let's explore. Okay, welcome back. I hope you've got your five rolls and your final number. So you're going to play against me and see if your number is lower than my number. So I roll first, I've roll to six. So my next number is 4,000. I've roll to five, so my number becomes 3,900 because I can take away 100. I've roll a one, so I'm taking away 10. So my number is 3,890. I've roll a three, so I'm taking away 1000. My number is 2,890. Lastly, I've rolled a two, so my number is 2,790 is your number lower, less than 2,790. If it is well done, you've beaten me. If it's not I've won. Check your number now, decide if you've won. Right, let's move on then. And we're going to look today at some function machines. So, we've got a number here. The number is 603, and I'm taking away 100. What number is going to come out the other side of my function machine, have a think. You know it, shout at a screen, 503, fantastic. I've taken away 100 to give me 500. Now, if you're feeling really confident, pause the screen now to work out what function is taking place in my function machine. You're not feeling so confident, don't worry we're going to look at it together. So, my original number that went into my machine, 7,040, the number that came out of my machine, 6,040. What happened in my machine? My machine took away 1000. If you look at the thousands column, 7,000 became 6,000 so I took away 1000. Now lets have a look at some number lines. So, here are my numbers on my number line. I've got 4,837, 5,837. What is changing between these two numbers? The thousands column, fantastic. Firstly, I'm going to work out the numbers that come here. Then I'm going to work out the numbers that come here, okay? So the number in my grid here is 4,837. What number is going to come here, if I take away 1000. You see it's going to give me 3,837. I'll take away another 1000. Well done, it's going to give me 2,837. Count with me then it's going to give me 1,837. Oh, what's going to happen. If there's no thousands here, my number would be 837. There's no thousands left. Now I'm going to go back from this number up to 5,837. Before I continue here, I put my five thousands here, my eight hundreds here, my three tens here. And my seven ones here? So this time I'm going this way on my number line. Am I going back in steps of 1000? Or am I going up in steps of 1000? Well done, I must be going up in steps of 1000 if am going back to this way in the number line. So I'm going to add another 1000 here. I'm going to have 6,837, add one more thousand here, I'm going to have 7,837. What I'd like you to do now, is if you're feeling really confident, like you to have a go of this number line here, look at what's happening between the numbers and see if you could continue down the number line here. If you're not feeling so confident, don't worry. We're going to go through it together now. I've made the number with deines, am not going to show you using the deines. I'm going to show you counting down the number line in steps of 100. Why am I doing it in steps of 100? Well, if we look at this number 6,353, 6,253, what's happening between these numbers. They're decreasing in hundreds, not tens, not thousands, the two and the three telling me that. They're in the hundreds column. So we're going to count down in our hundreds down on and below. Do you want to feel more confident when it comes to you having a go on your way, you can use deines and drawings of deines to help you. 6,153, 6,053. Remember I don't have any more hundreds to take away from, so I have to do some regrouping here. So it's going to become 5,963, 5,863, 5,763, 5,663 and 5,563. Okay. Your independent test today is how can you make a target number? So question one, you have got here and it uses place value grid. You can, if you want to join, deines on, if you don't want to, that's absolutely fine. Your three questions are here. Question two is very similar, but the number that you're subtracting from a different question three, you're going to have a go at using a function machine, same for question four. You're going to work out what the missing function was. Question five, you've got a number line, you need to have a go at completing that. Remember you can use deines if you want to. You don't have to. The same the question six, remember what you do. There's a missing number this side of your number line. Pause the video now to complete your task? Once you're finished, remember we go through the answers together. So, press play again on your video. Okay, welcome back. Let's go through the answers then. So for question one and under is 3021, but I wanted to take away 10, I'll get 3011 if I wanted to take away 100 from 3021. I'll get 2,921, that's because I need to regroup. There's nothing in the hundreds column here. So I have to regroup 1000 so that it becomes to 2000, the 10 hundreds so it becomes 900, 3021 subtract 1000 then is 2021. Question two, my number was 4305. Take away 10, I have to do some regrouping here to get me to 4,295. I take away 100, I'm left with 4,205. I take away 1000, I'm left with 3,305. Next, I'm looking at our function machine. 4,897 went in, 1000 was taken away from that, and it gave me 3,897. Question four, complete the following function machine. So we know the number 3,402 went into my function machine, and the number 3,392 came back out of it. What was the missing function? Well done, it was in fact 10 was taken away. We couldn't take away 10 and we would have to regroup. So this would become three hundreds and this would become nine tens. Question five, finish the number line. Remember, draw on the deines if it will help you. So here's our number here, we've got to work backwards here, okay? So we're going to come back, gives us from 4,335, 4,325, 4,315, 4,305, 3,995, 3,985, 3,975. And our last question, we have to let backwards down the number line here. And then we have to look at this number here. My number was 3,458, my number therefore I'm going down in steps of hundreds is 3,358, 3,258, 3,158, 3,058, 2,958. Then followed here, remember this was going down in steps of 100. So if I want to go from here to here, I must go up in a step of a hundred to give me 3,658. If you'd like to, please ask your parent or carer to share your work from today on Twitter, by tagging @OakNational and using #LearnwithOak. Great work today, I'm really, really impressed. Fantastic in fact, don't forget to go and complete your final quiz now to show all of the fantastic learning you've been doing today, and hopefully I'll see you again soon. Thank you, and bye bye.

Worksheet: Finding 10, 100 or 1000 less than a given number

Exit Quiz: Finding 10, 100 or 1000 less than a given number

Completed: Finding 10, 100 or 1000 less than a given number

In this lesson, we will be using our place value knowledge to find 10, 100 or 1000 less than a given number and considering how the digits change when we are required to regroup

Maths

Finding 10, 100 or 1000 less than a given number

Introductory Quiz

Video

Worksheet

Final Quiz

Lesson Complete