Lesson video

Hello there.

My name is Mr. Goldie, and welcome to today's maths lesson.

I'm sure you're going to enjoy it.

And here is today's lesson outcome.

So the outcome today is I can count forwards and backwards using three-digit numbers.

And here are our keywords.

So the first keywords are 100s boundary.

Can you say that? 100s boundary.

Brilliant.

And the next keyword is pattern.

Can you say that, pattern? Excellent stuff.

So let's look at what those keywords mean.

So the 100s boundary is the point at which the numbers change into 100s numbers or from one set of 100s to another.

So 98, 99, 100, 101, 102.

A pattern is when objects or numbers are arranged following a rule.

A pattern is a repeated set of numbers, shapes, or objects.

And we're going to be looking at some patterns in today's lesson.

Here's our lesson outline.

So the first part of the lesson is counting forwards and backwards in 10s.

And the second part of the lesson is counting forwards and backwards in 100s.

Let's get started.

In this lesson you will meet Sofia and Andeep, and they're going to be doing lots and lots of counting with you today.

Sofia counts in 10s from 100 to 200.

So try and join in with the counting.

Are you ready? 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200.

Andeep counts in 10s from 200 to 300.

And again, try to join in.

So we're gonna start from 200.

Are you ready? Counting in 10s.

200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300.

What do you notice? What is the same? What is different? So have a quick look at the numbers that Sofia has said and the numbers that Andeep has said.

Can you see anything that is the same? Can you see anything that is different? There is a pattern in the numbers.

So Andeep says, "The same 10s numbers are repeated.

"The 100s numbers change "when the 100s boundary is crossed." "This pattern is repeated for all numbers "when you count in 10s," says Sofia.

So anytime you're counting in 10s and you get to the 90s number, you get to 190, you cross a 100s boundary to get to the 100s.

So 190, 200.

290, 300.

And that's probably the trickiest part of counting in 10s.

Counting in 10s can be represented using base 10 blocks.

So count from 200 to 300.

And I know we've just done this count already, but it's good to practise it.

Are you ready? So let's start with 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300.

290 + 10 = 300.

And again, that's the tricky part of counting in 10s when we cross that 100s boundary.

So next we're going to be counting from 300 to 400.

And again, we're going to be using base 10 blocks to help us with our count.

So again, are you ready? Counting from 300, and we're counting in 10s all the way to 400.

And again, look at the representation of the base 10 blocks to help you.

Are you ready? So we start with 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400.

390 + 10 = 400.

And again, that tricky part is crossing over that 100s boundary.

Count from 400 to 500.

Are you ready? 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500.

Excellent.

Very well done if you kept up with that.

The tricky part is where the numbers cross a 100s boundary.

"90 + 10 = 100." Thank you, Andeep.

"490 + 10 = 500." And again, we've got that same pattern, haven't we? When we added 10 to 90, we cross a 100s boundary.

Andeep counts from 500 to 600.

Numbers are getting quite big now.

There's Andeep.

You ready to count with him? See if you can keep up.

So, "500, 510, "520, 530, 540, "550, 560, 570, "580, 590, 600." Excellent.

Very well done if you kept up with that.

"590 + 10 = 600," says Sofia.

Thank you, Sofia.

What number comes next? We're going to have a go at a couple of questions together and then you're going to have a go at a couple of questions on your own.

So what number comes next? So Sofia says, "740, 750, "760, 770." What number comes next? The answer should be 780.

Andeep says, "660, 670, "680, 690." Again, what number comes next? Slightly trickier, this one.

Got the answer? The answer should be 700.

What number comes next? So there's a couple of questions for you to try on your own.

So see if you can work out what number comes next.

And sometimes it's really helpful to count aloud, just like I did there.

So you might want to count aloud and work out what number comes next.

Pause the video and see if you can work out those two numbers.

And welcome back.

Let's see how you got on.

Let's see if you got the right answer.

The first count says 950, 960, 970, 980.

The next number should be 990.

Very well done if you got that one right.

The next count says 860, 870, 880, 890.

What number comes next? You should have said 900.

And again, it's crossing that 100s boundary, isn't it? That's the tricky bit.

Sofia counts back in 10s from 400.

So we're still counting in 10s, but this time we're counting back.

And see if you can keep up with Sofia.

And remember that tricky part when we're crossing that 100s boundary.

And that's going to come very, very quickly when we count back from 400.

Are you ready? So the first number will be, "400." And then, "390, 380, 370, "360, 350, 340, "330, 320, 310, 300." Wow, lots of counting in today's lesson.

Andeep counts back in 10s from 700 to 600.

Don't forget to use that pattern to help you work out the numbers.

So try and keep up with Andeep.

He's going to start from 700 and he's going to count back in 10s.

And don't forget that tricky part again near the beginning when we cross over that 100s boundary.

Are you ready? So we start from, "700, 690, "680, 670, 660, "650, 640, 630, "620, 610, 600." Very well done if you kept up.

Counting backwards in 10s can be represented using base 10 blocks.

So again, we're going to do a count.

And this time the base 10 blocks are going to help us with our count as well, going to help you see that representation.

Count backwards in 10s from 500 to 400.

So we've got there 500 represented in base 10 blocks, and we're going to count back in 10s.

We're going to subtract 10 each time until we get to 400.

So you ready to start counting? So we're gonna say 500, first of all.

So 500, 490, 480, 470, 460, 450, 440, 430, 420, 410, 400.

Very well done if you kept up there.

And again, remember the tricky part.

The tricky part is crossing over that 100s boundary when we go from 500 to 490.

The 100s number changes as well as the 10s number changing.

Count back in 10s from 600.

So this time we're going to be starting with 600 and we're going to be counting back in 10s.

Are you ready? 600, 590, 580, 570, 560, 550, 540, 530, 520, 510, 500.

"What 10s number would come next in the count?" That was a good question, Andeep.

What number would come next? So if we were still counting back in 10s from 500, what number would come next? Ah, Sofia says, "490 would come next in the count." So again, we're crossing over one of those 100s boundaries to the 100 that comes before.

And the 10s number changes and so does the 100s number.

What number is missing? So again, this is one where we're going to do a couple together and then you are going to do a couple on your own.

So what number is missing? So Sofia says, "880, 870, 860, 850." What number is missing? What number would come next? Well the answer would be 840.

We're not crossing over a 100s boundary.

We're just subtracting a 10.

We're counting back in 10s.

Here's Andeep.

Andeep's one is slightly trickier 'cause I think he might be crossing over a 100s boundary.

Let's have a look.

So, "830, 820, "810, 800." What number comes next? What number comes before 800? What 10s number comes before 800? The answer would be 790.

So the 100s number's changed and so has the 10s number because we've crossed a 100s boundary.

Here's a couple for you to try on your own to see if you can work out what number is missing.

Pause the video and see if you can work them out.

Welcome back.

Let's see if you got them right.

So our first count goes 990, 980, 970, 960.

Remember, sometimes it helps to count aloud.

The next number would be 950.

Well done if you got that one right.

And the next one again is slightly trickier because we're crossing over a 100s boundary.

So the count goes 930, 920, 910, 900.

The next number would be 890.

We're crossing over a 100s boundary.

Very well done if you got that one right.

Complete the number track.

So Andeep says, "What are the missing 10s numbers?" "Count forwards or backwards "to work out the missing numbers." Let's start from 350 and count back from 350.

We know we're counting in 10s.

So the number that comes before 350 would be 340.

And the number that comes before that would be 330.

Now let's look next at the number between 360 and 380.

So we could count back from 380 or count forwards from 360.

So the answer would be 370.

Let's count up from 380.

The 380 + 10 would be 390.

400 + 10 would be 410.

And 410 + 10 would be 420.

Here's one to try on your own.

So complete the number track.

There's our number track.

"What are the missing 10s numbers?" says Andeep.

And again, "Count forwards or backwards "to work out the missing numbers." So pause the video.

Can you work out the missing numbers on that number track? And welcome back.

Let's have a look, see whether you got the answers right.

So let's start off with the number that comes before 560.

If we counted backwards from 560 in 10s, what number would come next? We'd have the answer 550.

Let's try 560, add 10 this time if we're counting up in 10s.

What would the answer be? It would be 570.

590, and we're counting up in 10s.

We're counting forwards in 10s.

The answer would be 600.

Then 610 + 10 would be be 620.

And another 10 would be 630.

And if we carry on counting in 10s, we get the answer 640.

Very well done if you got all those correct.

And here is Task A.

So count forwards or backwards to find the missing numbers.

So work out what number comes next.

And again, it might help to say the numbers aloud.

Part two of Task A, complete the number tracks.

So work out the missing numbers.

And again, we're counting forwards and backwards in 10s.

So you might need to count forwards from numbers or backwards.

Can you work out the missing numbers? So pause the video and have a go at Task A.

And welcome back.

Let's look at those answers.

So part one of Task A, count forwards or backwards to find the missing numbers.

So the answer to A was 250, 260, 270, 280.

Very well done if you got those ones correct.

And there are the answers to part two.

So again, you might want to pause the video and have a go at marking your work and see whether you got those right or not.

So part two of our lesson is counting forwards and backwards in 100s.

Sofia counts in 100s.

So she's gonna start off at 100 and count up in 100s.

Are you ready to try and join in with her? See if you can keep up.

So she starts off with, "100." Next she says, "200." And then, "300, 400, 500, "600, 700, 800, 900." And then will come, "1,000." And 1,000 is actually a four-digit number.

It's made out of four digits.

We've got a 1000s digit there as well.

What do you notice? Do you notice anything? The ones and 10s digit don't change when you add 100 to a three-digit number.

So you can see there, the 10s numbers are always zero and the ones numbers are also always zero.

When you add 100 to 900, you get 1,000.

Andeep counts back in 100s.

So Andeep's going to count back in 100s from 1,000.

Try and keep up with him and see if you can say all the numbers.

Are you ready? Andeep starts off with, "1,000." And then he says, "900, 800, "700, 600, 500, 400, "300, 200, 100, zero.

Very well done if you kept up there.

The ones and 10s digit don't change when you subtract 100 from a three-digit number.

Andeep counts back in 100s from 600.

So he's gonna start from 600 and count back in 100s.

So Andeep starts off by saying, "600." "What other numbers will Andeep say?" Let's count back and see.

Next he would say, "500." And then he'd say, "400, 300, 200, 100, zero." Sofia counts from 400 to 1,000.

So she starts off on, "400." What other numbers will Sofia say? Pause the video and try and work out what numbers Sofia would say.

And welcome back.

Let's see whether you were right or not.

So hopefully you counted from 400 all the way to 1,000.

And you should have said, "500, 600, 700, "800, 900, 1000." Very well done if you kept up and you said all the numbers to 1,000.

Sofia starts on 40 and adds on 100 each time.

So she's not starting with a 100s number.

She's actually going to be starting on 40.

Try and keep count with Sofia if you can.

Are you ready? We're gonna add on 100 each time.

So the next number would be, "140." And then, "240, 340, "440, 540, 640, "740, 840, 940." What do you notice? The ones and 10s digits don't change when you add 100 to a three-digit number.

Can you see there? We're starting 40 and the next number is 140.

The 10s number hasn't changed.

It's still a four.

And the ones number hasn't changed.

It's still a zero.

And if we add on another 100, we get the answer 240.

And still that 10s number is a four.

It hasn't changed.

And the ones number is still a zero.

Andeep starts on 950 and subtracts 100 each time.

Again, see if you can keep up with Andeep.

Are you ready? So the first number's going to be, "950." And then, "850, 750, 650, "550, 450, 350, "250, 150, 50." And again, Sofia says, "The ones and 10s digits don't change "when you subtract 100 from a three-digit number." Sofia starts on 260 and adds on 100 each time.

"260," says Sofia.

She stops when she gets to 760.

Andeep asks, "What other numbers will Sofia say?" What do you think? What other numbers will she say? And again, see if you can count up with Sofia and see if you can say all those numbers.

And remember, she stops when she gets to 760.

Are you ready? So the first number is, "260." And next will come, "360, 460, "560, 660, 760." Oh, did you stop? Very well done if you did.

So those are the numbers that Sofia would've said.

And again, you can see the 100s digit changes.

The 10s digits and the ones digits don't change.

They stay the same.

Andeep starts on 770 and subtracts 100 each time.

So the first number Andeep's going to say is, "770." "What other numbers will Andeep say?" So pause the video and see if you can count back and see if you can work out what other numbers Andeep would say.

And welcome back.

So Andeep starts on 770 and he's subtracting 100 each time.

He's counting back 100.

Let's see what numbers you should have said.

So the first number was, "770." Next he should have said, "670, 570, "470, 370, 270, "170, 70." Very well done if you managed to say all those numbers.

Sofia starts on 23 and adds on 100 each time.

So here's, "23." That's the number that Sofia is starting with.

And she's going to be adding on 100 each time.

So see if you can keep up with Sofia and see if you can say the numbers.

Are you ready? So, "23, 123, 223, "323, 423, 523, "623, 723, 823, 923." Bit difficult to say some of those, weren't they? Very well done if you kept up.

What do you notice? "The ones and 10 digits don't change "when you add 100 to a three-digit number." The ones digit doesn't change.

It starts off as a three and it stays a three all the way through, because we're adding on 100, we're not changing the ones digit.

And again, the 10s digit doesn't change.

It's stayed as two.

Andeep starts on 971 and subtracts 100 each time.

Are you ready? "971, 871, 771, "671, 571, 471, "371, 271, 171, 71." Very well done if you kept up there.

Quite a mouthful, wasn't it? And again, Sofia is telling us, just reminding us, "The ones and the 10s digits don't change "when you subtract 100 from a three-digit number." So again, we're going to do two together and then you are going to try to do two on your own.

You ready? So what comes next? So Sofia's count is, "285, 385, 485, 585." What comes next? The answer would be 685.

Andeep says, "607, 507, 407, 307." What comes next? The answer would be 207.

Andeep was counting backwards in 100s.

And again that ones digit and that 10s digit does not change.

Now here's two to try on your own.

So what comes next? So again, it might help to say the numbers aloud as well.

Okay, can you work out what comes next? Pause the video and have a go at those two questions.

Back.

Let's see how you got on.

Let's see if you got the right answer.

So the first count goes 487, 587, 687, 787.

So we're counting up in 100s.

Next should come 887.

Very well done if you got that one right.

The other count goes 403, 303, 203, 103.

Bit of a tricky one this one.

What will come next in that count? So we're subtracting 100 each time.

The 100s digit is changing.

The other digits aren't changing.

So next comes three.

Very well done if you got that one right.

Complete the table.

So we've got there a table and it says 100 less, number, 100 more.

Andeep is saying, "What number is 100 less than 140?" There's 140.

We could use that to help us work out the answer.

So we subtract 100 and we get the answer, 40.

100 less than 140 is 40.

Let's start with 140 again.

And Sofia is asking, "What number is 100 more than 140?" So if we add 100 to 140, we get the number 240.

So 100 more than 140 is 240.

What's 100 less than 314? It would be 214.

What's 100 more than 314? The answer would be 414.

Remember it's just that 100s digit that changes.

The ones digit and the 10s digit does not change.

And then let's look at the last problem.

So we've got 877.

877 is 100 more than 777.

And 777, 100 less than that would be 677.

And here's a problem to look at on your own.

So complete the table.

And Andeep's asking you, "What are the missing numbers?" Okay, so pause the video and see if you can work out the missing numbers from that table.

And welcome back.

Let's see whether you got the answers right.

So let's start off with 845.

100 less than 845 would be 745.

100 more than 845 would be 945.

And our next number we've got, 116.

116 is 100 less than 216.

And 100 more than 216 would be 316.

Very well done if you got those answers correct.

And here's a problem with a giraffe.

Geoff is 433 centimetres tall.

That might seem very, very tall.

It's not that tall for a giraffe.

Grant is 100 centimetres taller than Geoff.

How tall is Grant? How would you work out the answer? And Sofia's here to remind us that, "The ones and 10 digits don't change "when you add 100 to "or subtract 100 from a three-digit number." So if Grant is 100 centimetres taller than Geoff, we'd have to add 100 centimetres on to Geoff's height to work out Grant's height.

So the calculation would be 433 centimetres + 100 centimetres equals.

What would the answer be? The answer would be 533 centimetres.

Remember it's just that 100s digit that changes.

So Grant is 533 centimetres tall.

Here's a problem for you to try on your own.

Still about Geoff.

We've still got Geoff the giraffe.

And Geoff is still 433 centimetres tall.

Gina is 100 centimetres shorter than Geoff.

How tall is Gina? And Sofia again is reminding you that, "The ones and 10s digits don't change "when you add 100 to or subtract 100 from "a three-digit number." So think about what the question would be and try and work out the answer.

Pause the video and have a go trying to solve that problem.

And let's see how you got on.

The calculation you should have done is 433 centimetres - 100 centimetres = 333 centimetres.

That's how tall Gina is.

She's 100 centimetres shorter than Geoff.

So very well done if you got the right calculation and very, very well done if you've got the right answer.

And now we're going to go on to Task B.

So in Task B, you're going to complete the number tracks.

So can you work out the missing 100s numbers? And again, don't forget to count forwards and backwards to try and work out what those numbers are.

Part two of Task B is complete the table.

So can you work out what 100 less than those numbers are and what 100 more than those numbers are? And sometimes you're not given the number.

You might be given 100 less than the number or 100 more than the number.

And then part three of Task B.

Can you calculate the height of the giraffes? So you've got there at the top three giraffes.

So you've got Grace.

She's 367 centimetres tall.

And Gwen is 444 centimetres tall.

And Gavin is 509 centimetres tall.

And underneath you've got six questions.

You've got to work out the height of those other giraffes.

So can you work out how tall Greg is, and how tall Guy is, and how tall Glenda is? So pause the video and have a go Task B, and very, very best of luck with it.

And welcome back.

Let's look at those answers and see how you got on.

So here are the answers for part one of Task B.

So you can see there that the 100s digits are changing.

The one's digits and the 10s digits don't change when you add or subtract 100.

So well done if you got those ones correct.

Here's part two of Task B.

So probably the most difficult calculation there was that very, very last one if you got on to that one.

So 100 more than a number is 206.

So the number must be 106.

And 100 less than 106 is six.

Well done if you got on to Task B and you managed to complete that table.

And here is part three of Task B.

So let's look at A.

A says Greg is 100 centimetres taller than Gavin.

How tall is Greg? Gavin was 509 centimetres tall and Greg is 100 centimetres taller.

We'd have to add on 100 centimetres.

And that gives us the answer, 609 centimetres.

That's how tall Greg is.

Greg is pretty tall for a giraffe.

Please feel free to pause the video and check to see whether you've got those answers correct.

And excellent work today.

Lots and lots of calculating today, lots and lots of thinking.

And hopefully you're feeling a lot more confident at counting forwards and backwards in 100s.

And finally, let's look at our lesson summary.

So when you count forwards or backwards in 10s, the 10s digit changes.

The 100s digit only changes when the 100s boundary is crossed.

The ones and 10s digits don't change when you add 100 to a three-digit number.

The ones and 10s digits don't change when you subtract 100 from a three-digit number.