Lesson video

Hello there, my name is Mr. Goldie and welcome to today's maths lesson.

I'm sure you're going to have lots of fun.

And here is the outcome for today's lesson.

I can find 10 more and 10 less than a number up to 200.

And here are our keywords.

So the keywords are multiple.

Can you say multiple? And hundreds boundary.

Can you say hundreds boundary? And let's look at what those words mean.

So a multiple is the result of multiplying a number by another whole number.

10, 20, and 30 are all multiples of 10.

2, 4, 6, and 8 are all multiples of 2.

The hundreds boundary is the point at which the numbers change into hundreds numbers, or from one set of hundreds to another.

So we've got there an example of 98, 99, 100, 101, 102.

So the hundreds boundary is the 100 where it changes from two-digit numbers into three-digit numbers.

And here's our lesson outline.

So the first part of the lesson, we're going to be finding 10 more and less than a multiple of 10.

And in the second part of the lesson, we're going to be finding 10 more and less than any number up to 200.

Let's get started.

In this lesson, you will meet Jacob and Aisha, and Jacob and Aisha are going to be helping you with your work today.

Jacob and Aisha are adding and subtracting 10 to multiples of 10.

"What tens number comes after 70?" Says Aisha.

80 comes after 70.

"What tens number comes before 100?" Says Jacob.

90 comes before 100.

Jacob and Aisha look at multiples of 10 greater than 100.

"What tens number comes before 110?" Asks Aisha.

What tens number does come before 110? You can use the number line to help you work out the answer.

And it is 100.

100 comes before 110.

"What tens number comes after 170?" Says Jacob.

What do you think? What tens number comes after 170? 180.

180 comes after 170.

You can represent numbers using base 10 blocks.

100 looks like this, 10 looks like this, and one looks like this.

You can use base 10 blocks to help you add a 10.

You can also use base 10 blocks to subtract a 10.

Jacob calculates 70 subtract 10.

I'll start with 7 tens.

So 7 tens equals 70.

So Jacob's going to start with 7 tens.

He subtracts a 10.

Jacob uses a number line to represent the calculation.

So he starts from 70 and he subtracts 10, and that gives the answer 60.

70 subtract 10 equals 60.

Jacob calculates 40 add 10.

"I'll start with four tens," says Jacob.

I've got four tens.

Four tens equals 40.

He adds a 10.

And Jacob uses a number line to represent his calculation.

So it starts from 40 and he adds on 10, and that gets him to the answer 50.

40 add 10 equals 50.

Jacob calculates 130 add 10.

So we're looking at numbers now which are bigger, which are larger than 100.

"I'll start with 13 tens," says Jacob.

So he's got 100, 10 tens, and 3 more tens.

There are 13 tens altogether.

He adds a 10.

What number do you think Jacob has got now? Well, he uses a number line to represent the calculation.

So he starts at 130, he adds 10 and that gives him the answer 140.

13 tens add 1 ten equals 14 tens.

130 add 10 equals 140.

Jacob calculates 130 subtract 10.

"I'll start with 13 tens," says Jacob.

130 is made up of 13 tens.

He's represented 13 tens, or 130.

So it's made up of 100 and 3 tens.

He subtracts a 10.

What number is Jacob left with what? Well, Jacob uses a number line to represent the calculation.

So you could find 130 on the number line and subtract a 10, and the answer would be 120.

13 tens subtract 1 ten equals 12 tens, or 130 subtract 10 equals 120.

What do you notice? 70 subtract 10 equals 60.

130 subtract 10 equals 120.

40 add 10 equals 50.

130 add 10 equals 140.

Do you notice anything? Let's have a look.

Well, Jacob says, "The ones digit does not change." We're starting with a zero as the ones digit, and we're still left with a zero at the end after we've subtracted the 10, or added the 10.

Only the tens digit changes.

So we've got there, 70 subtract 10 equals 60.

So it's only the tens digit that changes.

Do any other digits change? Sometimes the one hundreds digit also changes.

So in the calculation 100 subtract 10, we get the answer 90.

So the one hundreds digit has changed.

Calculate 100 subtract 10.

100 is equal to 10 tens.

So let's split up that 100 into 10 tens.

Let's subtract a 10, and we're left with 9 tens, or 90.

And we can represent that calculation on a number line as well.

So a hundred subtract 10 equals 90.

Calculate 100 add 10.

Let's start with a hundred or 10 tens, and it's add a 10.

So 100 add 10 equals 110.

And we can represent that calculation on the number line as well.

So we start from 100 and we add on ten.

100 add 10 equals 110.

And here's a couple of calculations for you to try yourself.

So calculate 150 subtract 10, and calculate 150 add 10.

What do you think the answers will be? If you have base 10 blocks, you may want to use those to help you work out the answers.

So pause the video and have a go at those two calculations.

And welcome back.

How did you get on? Did you manage to answer both questions? Let's look at that first one.

So the first one was calculate 150 subtract 10.

So if we subtract a 10, we're left with 140, and we can represent that calculation on the number line as well.

So 150 subtract 10 equals 140.

What's 150 add 10? 150 add 10 equals 160.

And we can also represent that calculation on the number line as well.

The 150 add 10 equals 160.

Very well done if you've got both those calculations correct.

Let's move on to a missing number problem.

So Jacob tries to find the missing minuend.

So in this subtraction calculation, it's the minuend that is missing.

Something subtract 10 equals 110.

What's the missing number? Let's start with 110.

Let's represent 110 using base 10 blocks.

Is the minuend larger or smaller than 110? What do you think? The minuend is 10 greater than 110.

So remember, we're starting with the minuend, we subtract a 10 and we're left with 110.

So the minuend must be bigger than 110.

Jacob solves the problem using addition.

What is 110 add 10? So if we add the 10 back on again, we'll get the missing minuend.

So let's add a 10 to our base 10 blocks.

We add a 10, and we're left with 100 and 2 tens, and we can represent that problem on the number line as well.

So 110 add 10 equals 120.

120 subtract 10 equals 110.

Now here's one to try and solve on your own.

Jacob tries to find the missing addend.

So a number add 10 equals 170.

He represents the problem using base 10 blocks.

So we've got there 100 and 7 tens.

"Is the addend larger or smaller than 170?" Asks Jacob.

"The addend is 10 less than 170," says Aisha.

How would you solve the problem? What do you think the answer is? What is the missing addend? Pause the video and see if you can solve the problem.

And welcome back.

Did you manage to find the missing number? Let's have a look to see if you were right.

So Jacob solves the problem using subtraction.

What is 170 subtract 10? So let's subtract a 10 from our base 10 blocks.

What are we left with? We're left with 100 and 6 tens.

We can represent the problem using a number line as well.

Again, let's start from 170 and subtract back a ten.

170 subtract 10 equals 160.

So 160 add 10 equals 170.

Very well done if you managed to solve the problem.

And let's move on to our task, so Task A.

Part one of Task A, complete the calculations.

Use base 10 blocks or a number line to help you.

So there are some subtraction calculations and some addition calculations.

And part two, got some missing number problems. So we've got there either a missing minuend or a missing addend.

Can you try and work out the number that is missing from those calculations? So pause the video and have a go at Task A.

And welcome back.

How did you get on? Did you manage to find all the missing answers? Did you? Very well done if you did.

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

So we've got there, 80 subtract 10 equals 70, 80 add 10 equals 90, and there's also 180 subtract 10 that equals 170, and 180 add 10 equals 190.

You may have spotted the relationship between those calculations.

And here's the answers to part two, our missing number problems. So we've got there 150 subtract 10 equals 140, 130 add 10 equals 140.

Very well done if you got on to part two of Task A and managed to find some of those missing numbers.

And let's move on to part two of our lesson.

So part two of our lesson is finding 10 more and less than any number.

Aisha calculates 73 subtract 10.

"I'll start with 7 tens and 3 ones," Says Aisha.

So she's going to represent the problem using base 10 blocks.

She subtracts a 10 to work out the answer.

Aisha uses a number line to represent the calculation.

So this time she starts on 73.

She is going to do the calculation 73 subtract 10.

What is 73 subtract 10? So we subtract a 10 and we get the answer 63.

73 subtract 10 equals 63.

Aisha calculates 145 subtract 10.

I'll start with 100, 4 tens and 5 ones.

So Aisha represents her problem using base 10 blocks.

She subtracts a 10.

What number do you think she's left with this time? So Aisha uses a number line to represent the calculation.

So she starts this time on 145.

She subtracts a 10 and gets the answer 135.

145 subtract 10 equals 135.

You may have spotted something already, we'll have a look at that later.

Aisha calculates 94 add 10.

What is 94 add 10? "I'll start with 9 tens and 4 ones," says Aisha.

So she represents the problem using base 10 blocks.

She adds a 10.

So the 9 tens become 10 tens, and 10 tens is equal to 100.

Aisha uses a number line and crosses the hundreds boundary.

So she starts from 94 and she adds on a 10, and that gets her the answer 104.

So Jacob says, "90 add 10 equals 100, 94 add 10 equals 104." Aisha calculates 177 add 10.

I'll start with 100, 7 tens and 7 ones.

So Aisha represents that 177 using base 10 blocks.

She adds a 10, so she adds 10 more.

You might be able to see what the answer is already.

Aisha also uses a number line to represent the calculation.

So she starts this time on 177, that's where 177 would be on the number line, and she adds on a ten.

177 add 10 equals 187.

So Jacob says, "177 add 10 equals 187." What do you notice? 73 subtract 10 equals 63.

145 subtract 10 equals 135.

94 add 10 equals 104.

177 add 10 equals 187.

Think about what we noticed last time when we were adding 10 or subtracting 10 from a multiple of 10.

When you add or subtract a 10, the ones number does not change.

So the ones number doesn't change.

When you add or subtract a 10, the tens number changes.

So the tens number changes, but the ones number does not change when you add or subtract a 10.

The hundreds number also changes if you cross a hundreds boundary.

So can you see there, that 94 add 10 equals 104? 104 subtract 10 would equal 94.

So sometimes the hundreds number also changes, but only if you cross a hundreds boundary.

What is 91 add 10? So let's represent 91 using base 10 blocks.

Let's think about representing 91 add 10 on a number line.

There's 91, we add on a 10, we get to the answer 101.

91 add 10 equals 101.

What is 101 subtract 10? 101 subtract 10 would equal 91.

Here's one to have a go on your own.

93 add 10.

There's 93, represented using base 10 blocks, and there's a number line.

Now have a go at that calculation, 93 add 10.

You can use a number line to help you or you can use base 10 blocks to help you if you've got them.

Pause the video and have a go.

Can you work out the answer to the calculation? Welcome back.

Let's see how you got on.

Let's use our number line representation first of all.

Let's start with 93 and let's add on a 10.

93 add 10 crosses over that a hundreds boundary, and the answer would be 103.

If we use our base 10 blocks, we've got 9 tens.

If we add a 10 to our 9 tens, we'd end up with 10 tens.

10 tens is equal to 100, so the answer would be 103.

The calculation crosses the hundreds boundary.

So that makes it slightly trickier when we're crossing over the hundreds boundary, but remember that ones digit is not going to change if we're adding or subtracting a 10.

What is 109 subtract 10? So here's another calculation to try on your own.

So you can represent the problem using base 10 blocks or a number line.

So again, pause the video.

Can you work out the answer? What is 109 subtract 10? And welcome back.

Did you manage to solve the problem? Let's have a look to see how you got on.

So let's use our number line representation first of all.

We'll start from 109, just one less than 110, and we're going to subtract a 10, and that again crosses the hundreds boundary.

109 minus 10, and the answer would be 99.

So remember, that ones number doesn't change.

109 subtract 10 equals 99.

So here's our base 10 blocks, that 100 would change from 10 tens into 9 tens.

The calculation crosses the hundreds boundary.

And again, that's what makes it slightly tricky.

Jacob completes the table.

I need to add and subtract 10.

So 165 subtract 10 equals 155.

So 10 less than 165 is 155.

What's 10 more than 165? 10 more than 165 is the same as 165 add 10, which equals 175.

So 10 more than 165 is 175.

Underneath we've got the number 118.

What is that 10 more than, or what is 10 less than 118? 108 is 10 less than 118.

And what is 10 less than 108? 98 is 10 less than 108.

So our last number in there would be 98.

Complete the table.

So can you work out what the number in the middle should be? Work out what 10 less that number should be, and what 10 more than that number should be.

So pause the video and can you complete the table? And again, you can use base 10 blocks or a number line to help you work out the answer.

And welcome back.

Let's look at those answers.

So 10 less than 113 is 103, 10 more than 113 is 123, 89 is 10 less than 99, and 10 more than 99 is 109.

136 is 10 more than 126, and 10 less than 126 is 116.

Very well done if you managed to answer some of those questions, and excellent work if you managed to find all the answers.

Jacob and Aisha live in the same road.

"I live at house number 141," says Jacob.

My house number is 10 more than Jacob's.

Which house does Aisha live at? What do you think? How would you work out the answer? Let's use a number line representation to help us work out the answer.

So Jacob's house is 141.

So if we add 10 to 141, we get the answer 151.

So Aisha lives at 151.

141 add 10 equals 151.

Jacob and Aisha solve problems by adding and subtracting 10.

Paul, the giant panda, has a mass of 85 kilogrammes.

Peter is 10 kilogrammes heavier than Paul.

How heavy is Peter? I wonder how you'd work the answer out.

How would you calculate Peter's mass? So how heavy is Peter? So 85 kilogrammes add 10 kilogrammes equals how many kilogrammes? Let's use a number line representation to help us work out the answer.

Let's start with 85, and we're going to add on a 10.

So 85 add 10 equals 95.

Remember that ones number doesn't change when we're adding or subtracting a 10.

So 85 kilogrammes add 10 kilogrammes would equal 95 kilogrammes.

And here's one to try on your own.

Polly, the panda, has a mass of 107 kilogrammes.

Poppy is 10 kilogrammes heavier than Polly, whereas Pip is 10 kilogrammes lighter than Polly.

How would you calculate their mass? How heavy is Poppy? How heavy is Pip? Pause the video and try to work out how heavy each panda is.

And welcome back.

Did you manage to solve both problems? Did you find out Poppy's mass and Pip's mass as well? Let's have a look at how you should have calculated them.

So Poppy is 10 kilogrammes heavier than Polly.

So the calculation you should have done is 107 kilogrammes plus 10 kilogrammes equals 117 kilogrammes.

So Poppy's mass is 117 kilogrammes.

Pip is 10 kilogrammes lighter than Polly.

The calculation you should have done is 107 kilogrammes subtract 10 kilogrammes equals 97 kilogrammes.

So Pip's mass is 97 kilogrammes.

Well done if you've managed to find both answers.

And let's look at Task B.

So the first part of Task B, you've got to complete the table.

So you're given some numbers, you've got to work out what 10 more than the numbers are or 10 less than the numbers are.

And sometimes you're given the number that is 10 less than the number, or 10 more than the number.

Part two, you've got to work out the mass of the pandas.

So Pat has a mass of 112 kilogrammes.

Can you work out Peppa's mass, and Priya's mass, and Perry's mass, and Pedro's mass? And the last problem is, the Oak Academy children live on the same road.

So Izzy lives at number 96, Jun lives at number 114, and Jacob lives at number 141.

Use the clues to work out where the other children live.

So can you work out where Lucas lives, and Andeep lives? Can you also work out Alex's house number, and Laura's house number, and Sam's house number, and Sofia's house number using the clues? So you've got three different problems there to look at.

So pause the video and have a go trying to solve those problems. And welcome back.

And let's take a look at our answers.

So for the first part of Task B, there are the answers.

So the first number was 164.

10 less than 164 is 154, and 10 more than 164 is 174.

Here's part two of Task B.

So working out the mass of the pandas.

So Peppa's mass was 122 kilogrammes, Priya's mass was 132 kilogrammes, Perry had a mass of 102 kilogrammes, and Pedro's mass is 92 kilogrammes.

So very well done if you managed to solve all those problems. And on to the third part of Task B.

So here are the house numbers.

So Lucas lives at number 104, Alex's house number is 131, Sam's house number is 94, Andeep's house number is 106, Laura lives at number 86, and Sofia's house number is 124.

Excellent work today.

I hope you're feeling much more confident at adding and subtracting 10 to different numbers, and especially when you're crossing that hundreds boundary, which is the tricky part.

And let's look at our lesson summary for today.

So when you add or subtract a 10, the tens number changes, but the one's number does not change.

The hundreds number also changes if you cross a hundreds boundary.