Lesson video

Hello, everybody.

I'm Mrs. Crane and welcome to today's lesson.

In today's lesson, we're going to be learning how to round numbers to the nearest multiple of 100.

What's the weather like where you are today? It's a really gloomy day here but it's actually quite warm outside.

In a moment, I will go through all of the equipment that we will need for today's lessons so please don't worry about getting anything just yet.

If you can, please turn off all of the notifications on your phone, tablet, or whichever device you are using for today's lesson.

And if you can, try and find somewhere in your home that's nice and quiet and distraction-free so that we can get started on today's lesson together in a moment.

When you're ready, let's begin.

Okay, then, our agenda today.

We're going to be using a counting stick.

We're then going to be exploring and picking a number.

Then we're going to be looking at number lines.

And then we're going to be doing our independent task today, which is can you round a number to the nearest 100? So, today's lesson, you will need a pencil and some paper.

If you don't have those, please pause your video now to go and get those things before we make a real start.

Okay, welcome back.

Let's get started.

So, when do we need to round? And today, I'm thinking particularly when do we do need to round to the nearest multiple of 100? I can think of examples where I might need to round to the nearest multiple of 10 but 100's different one.

So, what I was thinking, I was thinking if I went on a holiday and I was on a plane and my journey might be 372 kilometres long or miles away.

Now, I wouldn't generally say it's 372, I would say it's about 400 miles or 400 kilometres away, depending on which measure that we're using.

Now, again, if I was off on holiday, I might be off in the car.

Might be going on a long drive and I might say, "Oh it's around 100 miles away," but it might actually be 94 miles away.

I would tend to round up to the nearest multiple of 100 when I'm talking about a long, long distance.

And then I was thinking, if I was going to go buy a car, my car is going to cost me 1,741 pounds, I wouldn't say it's going to cost me 1,741 pounds.

I'd probably say it's going to cost me 1,700 pounds and round it down to the nearest multiple of 100 just because it makes it a bit more clearer when you're explaining it to somebody.

They can hear it more clearly and we tend to round in those kind of situations.

Can you think of another example why we might round to the nearest multiple of 100? Try to think.

Well done, if you can.

There are lots more examples, so my three are just three small examples that I could think of.

So, let's get started with how we round to the nearest multiple of 100, then.

Right then.

We're going to get started with looking at the number 376.

Now, the first thing we need to do is identify the two nearest multiples of 100 to this number here.

So we're going to do that, and we are going to use our counting stick today to help us begin with.

So, my two nearest multiples of 100 are 300 and 400, because if I was looking at the multiples of 100 that it sits between, these are the two.

So I can put that into my sentence here.

The nearest multiples of 100 are 300 and 400.

So, I know my answer's either going to be 300 or 400.

If I get a different answer, then I've got confused somewhere.

So, have a look at the next thing I need to do.

The next thing I need to do is mark on roughly where this number is going to go between 300 and 400.

Now, each of these is worth ten when we're counting between two hundreds.

So, I'm going to not be able to mark on exactly on my number line but that's okay.

We don't need to mark on exactly.

We can mark on 310, 320, 330.

Well done, if you're counting on with me.

340.

350.

360.

370.

Now, 376 is going to be somewhere around the middle of that, a little bit closer to the red.

So, to help me do that, I can imagine halfway through my number line is 350.

Now, why have I marked that on to help me when I've come to mark it on here? Why would that be helpful? Well, it's the halfway point, isn't it? So that halfway point helps me out in knowing how I mark correctly, and 376 is definitely further and closer to 400 than it is to 300.

So, I know it has to be past 350, because I know 376 is higher than 350.

So, it's just going to help me out with knowing if I've marked on roughly into the right place.

So, we know that if we are looking at rounding to the nearest hundred, multiple of 100, we need to look in our tens column, and in our tens column, if it's 4 or less, we have to round it down.

If it's 5 or more, we round it up, in the tens column when we're rounding to the nearest hundred.

Okay? So, we've marked all of that on, we think our number's around about here, absolutely.

That is where our number is, so, because we've marked that on, because we know about looking in our tens column, does our number, 376, round up to 400, or down to 300? What do you think? Absolutely.

It rounds up to 400.

So I can complete this sentence here.

I can say 376 rounded to the nearest hundred is 400.

You can clearly see it's closer to 400 than it is to 300.

Again, we can use here, this notation here.

This shows that it is approximately equal to 400.

So it says, "376 is approximately equal to 400 when we're rounding." It doesn't have straight equal signs like this because it's not actually equal to it, so it has wavy lines to say it's approximately equal to it when we're rounding.

Okay, next number then, is number 1453.

Again, the first thing we're going to do is identify the two nearest multiples of 100.

This time, our number is a 4 digit number, but that doesn't matter.

We're not going to let that throw us.

We're still going to put our two nearest multiples of 100 here.

We're going to go for 1400 and we're going to go for 1500.

These are both two multiples of 100.

So, we can say now that our nearest multiples of 100 are 1400 and 1500.

Next thing we're going to do.

I'm going to mark on that halfway point.

My halfway point between these two numbers is number 1450.

It goes here, halfway across our counting stick.

Next thing I can do then, is mark on where my number goes.

1453.

Now, I know that if I'm rounding to the nearest multiple of 100, I need to look in my tens column to see what the digit is to decide whether I need to round it up or down.

Now, because it's a five, I know I need to round it up.

We can also clearly see that it sits closer to 1500 than it does to 1400.

So, I can say 1453 rounded to the nearest hundred is 1500.

And again, I can show that using my symbol, my approximately equals symbol.

Next one then.

3017.

First, we've got to identify those two nearest multiples of 100, which are going to be 3000 and 3100.

We can put that into our sentence here.

Next, we need to mark on our number, 3017.

Oh, before we do that, we're going to use this to help us.

3050, we're going to mark that on.

That's our halfway point.

Is 3017 this side or this side of our halfway point? Yep, it's definitely this side.

So, if I mark it on, I know it's roughly here because I know I have 3010, 3020.

It's not quite 3020, but it's further than 3010, so we've marked on 3017 here.

Does it round up to 3100 or down to 3000? Yep, clearly rounds down to 3000.

It's clearly closer, and if I look that the digit in my tens column, it's a one.

I know that if it's four or less, I need to round it down, so I can say 3017 rounded to the nearest hundred is 3000.

Again, I can show it using that notif.

that equation symbol there.

Now, if you're feeling confident, I'd like you to pause the video, and have a go at that, firstly identifying where the two nearest multiples of 100 are, for the number 7537, then identify where that number sits on our counting stick, then have a go at deciding whether it rounds to up or down.

If you're not feeling so confident, don't worry.

We're going to do that together now.

So, the number was 7537.

So, our two nearest multiples of 100 are 7500 and 7600.

Going to mark on those into my sentence here, then I'm going to mark on my halfway point: 7550.

Now, 7537 isn't as far as 7500, so I need to count up in my tens until I get roughly nearby, so, seven thousand, five hundred and ten, seven thousand, five hundred and twenty, seven thousand, five hundred and thirty, and seven thousand, five hundred and forty.

So, it's going to sit roughly here when we mark it in.

Absolutely.

Seven thousand, five hundred and thirty-seven.

Now, is 7537 closer to seven thousand, five hundred or seven thousand, six hundred? Well, looking at it, I can see it's clearly closer to 7500 and if I look in my tens column, it's a 3, I know that if it's 4 or less, I round it down, so I can say 7537 rounded to the nearest hundred is 7500.

Again, I can put it in here.

Now, before we have a go a pick a number today, I want you to have a go at that "Marking my work." So, I've rounded the number one thousand, seven hundred and fifty one, to the nearest hundred and my answer is 1851.

What to do now is work out if, "Yes, I'm correct," or "No, I'm wrong." And, my challenge today is can you explain your choice? Either yes or no.

Pause the video now to have a go at my quick question.

Okay, welcome back.

Have you marked my answer? Was I correct, or was I incorrect? Well, first thing we need to do is mark on the two multiples of 100.

1700, 1800.

My answer was 1851, can it EVER have been correct? It can't have been because it's not a multiple of a hundred, so if I'm rounding to the nearest hundred, my answer isn't a multiple of one hundred, I've gone wrong.

So, then needed to mark on my number, which is 1751.

It is a bit of a tricky number because it's got a five in that tens column, but I know that if there is a five in my tens column and I round to the nearest hundred, I need to round up, so my answer should've been, 1800.

Clearly seeing here that there is that five in the tens column, I round it up, NOT to this number here.

So, unfortunately, I got it wrong, and I've got an answer that isn't even a multiple of 100 in my answer box, so, let's make sure that we don't let that happen to us today.

Right then, in a moment, we're going to do "Let's Explore" which is pick a number.

Okay, I'm going to hide myself a moment so you can see your counting stick.

So, you've got a counting stick at the top here, and you've got a box here with lots of different numbers in it.

My challenge row today is this bottom row here, so if you feel like doing a challenge today, have a look at these numbers here.

If you don't want to do a challenge, that's okay.

Because then you can have a guess from these boxes here.

Now, what I'd like you to do is firstly, on your piece of paper, mark on, and draw on a counting stick, mark on your two nearest multiples of 100, mark on your number, and decide whether your number rounds up or down to the nearest multiple of 100.

Pause the video now to have a go at today's "Let's Explore." Okay, welcome back.

What we're going to do now is have a look at what makes these questions, the bottom row here, more challenging.

So, the numbers on our bottom row are Four thousand, nine hundred and ninety-nine, two hundred and fifty, and three thousand, nine hundred and fifty.

Now, I know here, the two nearest multiples of 100 are going to be 4900 and 5000.

We're bridging that gap up to the next multiple of 1000, which is also the next multiple of 10.

And here, with 250 and 3950, what made them harder was the fact that they ended in 50's.

That fifty and that five is always halfway, but we know that if it ends in that- well, not if it ends in that five, sorry.

If there's a five in that tens column, then we still round it up.

So, although it looks like it's about halfway, it still rounds up to the nearest multiple of 100, which is the higher multiple of 100.

When it's got a 50 in it and we're rounding to the nearest multiple of 100.

Okay? So, next, what we're going to do is we're going to look at number lines.

They look very similar to a counting stick, but there are some slight differences because we don't have the colours to help us block it out.

Now, my number is 8327.

Again, I'm going to mark on those two nearest multiples of 100.

So, I'm going to have 8300 and 8400 here.

Now, I need to mark on roughly about 8327, guys.

It goes roughly here, because I can say that's 8310, that's 8320, that's 8330.

So, it's roughly here.

We can't put it on exactly because that would take us quite a long time to work out exactly where it needs to go, and we don't need to do that.

Now, does it round up or down from just looking at it? Which is it closest to? Definitely closest to 8300, and if I look in that tens column, it's got a two, so I know it needs to round down.

So, my answer is 8300.

Next number, then.

3047.

Again, there's no hundreds in this column here, so my first multiple of 100 must be 3000.

My second multiple of 100 would be 3100.

3047; I know that's very close to 3050, so when I mark it, I'm going to mark it on here.

Now, have I marked on here? No, I haven't, there's a four in that tens column, so I know I need to round it down to 3000.

If I look at it, I can see it's closer.

Now, if you're feeling confident, the last example on the number line today before you have a go on your own, pause the video now.

If you would like a little bit of extra support on this one, we'll go through it together.

So, my number is 4982.

My two multiples of 100 are 4900, and 5000.

Okay? So, that's the next multiple of 100 is also a multiple of 1000.

Now, I need to mark on 4982.

I know it goes quite close to 5000, because it has 82 in it, so it goes about here.

That would be 4980, 4990.

So, 92, roughly here.

82, sorry, roughly here.

Now, if I look at that, I can see it clearly rounds up to five thousand.

There's an eight in the tens column, and I know that if there's five or more in the tens column, I know I need to round up to the nearest multiple of 100.

Okay, your independent task today is, "Can you round a number to the nearest 100?" Going to hide myself on the net so you can see what your task is.

So, the first thing I'd like you to do on questions one and two is locate the number.

You've got your nearest multiples of 100 written in for you.

Then I'd like you to decide which is the nearer multiple of 100 and write in your answers here and here.

For questions 3, 4, 5, and 6, firstly, you need to use number lines and write in the two closest multiples of 100.

They haven't been written in for you on these questions.

Then, you need to locate your number, and then you need to decide which is your closest multiple of 100 and write in your answer.

Same questions on 5 and 6.

Then, once you've finished, when we'll go through the answers together.

There is a challenge question today.

My challenge is round 5297 to the nearest ten, then round it to the nearest hundred.

What do you notice? Can you suggest any other numbers that are like this, and why does this happen? Pause the video now to complete your task.

Don't forget, we'll go through the answers together at the end, so remember to resume your video once you've finished.

Okay, welcome back.

I'm back, so you can see me! So, let's have a look at our answers then.

For question 1 and 2, first number was 62.

We've got 0 and 100 marked on already for us.

60 goes roughly here, so we know 62 is about there.

It rounds up to 100.

807, we've got 800 here and 900 here.

807 goes roughly here, so it rounds down to 800.

7059.

Firstly, we need to mark on our two multiples of 100 which are 7000 and 7100.

7059 is roughly here, does it round up or down? Well done, it rounds up to 7100.

Three thousand, six hundred and fifty five.

We've got 3600, 3700.

3655 is roughly here.

Does it round up or down? Well done, it rounds up to 3700.

2850.

We've got 2800 and 2900.

Now, this is one of those tricky ones, which is exactly halfway.

If it's got a five in the tens column, we know we need to round it up.

So, although it's exactly halfway between the two of them, it is technically closer to 2900, so it goes up to 2900.

And nine thousand, two hundred and sixty-four.

Oop, it wanted to spin around twice.

We've got 9200 and 9300.

9264 goes roughly here, about there.

Does it round up or down? Fantastic, it rounds up to 9300.

Right then, let's look at my challenge today.

So, my challenge was, round the number 5297 to the nearest 10.

Do that first, then.

So, 5290, 5300 is my next multiple of 10.

So, mark it on.

It goes here.

Does it round up or down? It rounds up to 5300.

Okay, let's see what happens, then if we round it to the nearest 100 and see what we've noticed.

So, I'm going to put the two nearest multiples of 100.

Here's 5200.

Here's 5300.

Let's mark on our number.

5297's roughly here.

We can't quite mark it on as close as we want to.

Does it round up or down? Absolutely, it also rounds up to 5300.

So, what I've noticed is, this number rounds up to the same multiple of 10, which is the same multiple of 100.

Did you manage to think of any other numbers like that? Well done if you did.

Okay, if you'd like to, please share your.

Please ask your parent or carer to share your work today on Twitter by tagging @OakNational and the hashtag Learn with Oak.

I've been really, really impressed with your rounding today, well done! Don't forget to complete that quiz to show everything you've worked really hard towards, and hopefully I'll see you again soon for some more maths.

Thank you and bye bye!.