Lesson video

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

I'm sure you're gonna have lots of fun.

And here is our lesson outcome.

So, our lesson outcome is, I can use known facts to help me solve partitioning problems. And here are the key words for today.

I'm going to say the keyword, can you repeat it back to me? So, the first keyword is double.

And the next keyword is multiple.

Excellent.

So, what do those words mean? Well, double means to become twice as many.

Double two is equal to four, and a multiple is the result of multiplying a number by another whole number.

So, 10, 20, and 30 are all multiples of 10, and 2, 4, 6 and 8 are all multiples of 2.

And here's our lesson outline.

So, in the first part of the lesson, we're going to be using multiples of 10 totaling 100.

And in the second part of the lesson we're going to be using doubles and near doubles of multiples of 10.

Let's get started.

In our lesson today, you will meet Sophia and Andeep, and they're going to be doing lots and lots of calculating with you today.

Sophia and Andeep think of multiples of 10, that sum to 100.

So, 90 add 10 equals 100.

They have a sum of 100 and they're both multiples of 10.

So, 9 tens, add one 10 equals 10 tens or 100.

Sophia says, "80 add 20 equals 100." 8 tens add 2 tens equals 10 tens or 100.

Sophia and Andeep think of other multiples of 10 that equal 100.

"70 add 30 equals 100," says Andeep.

7 tens add 3 tens equals 10 tens.

Sophia says, "60 add 40 equals 100." 6 tens add 4 tens equals 10 tens.

60 add 40 equals 100.

Is there another way of making 100 using two multiples of 10? What do you think? Is there another way of making 100 using multiples of 10? How else could you make 100? Can you think of another possible way of making 100? Pause the video and see if you can think of another way of making 100.

And welcome back.

Did you manage to find the last way of making 100? So, you should have said, 5 tens add 5 tens equals 10 tens, or 50 add 50 equals 100.

Very well done.

If you found the last way of making 100, using two multiples of 10.

Andeep wants to find the missing number.

So, we've got a bar model with 300 being the sum and 280 being one of the parts.

"What do I add to 280 to equal 300," asks Andeep.

"I know 80 add 20 equals 100," says Sophia.

So, 280 add 20 equals 300.

Let's represent that using base 10 blocks.

So, we've got that 280 add 20, and that 80 add the 20 makes another 100.

280 add 20 equals 300.

Sophia wants to find the missing number.

So, this time the sum is 400 and one of the parts is 360.

"What do I add to 360 to equal 400?" asks Sophia.

What number fact could she use to help her? "I know 60 add 40 equals 100," says Andeep.

So, 360 add 40 equals 400.

So, Andeep saying the missing part is 40.

Let's represent that using base 10 blocks.

So, we've got there 360, 3 hundreds and 6 tens, add 40 or 4 tens.

And those 6 tens add those 4 tens would make between them another 100.

So, our missing part is 40.

Andeep wants to find the missing number.

This time, the sum is 500 and one of the parts is 490.

I wonder what the missing part is.

"What do I add to 490 to equal 500?" asks Andeep.

"I know 90 add 10 equals 100," says Sophia.

So, 490 add 10 equals 500.

And again, let's represent that using base 10 blocks.

So, we've got there 490, 4 hundreds and 9 tens, add 1 ten.

And those 9 tens add that 1 ten go together to make 100.

So, the missing part was 10.

We had to add on 10 to 490 to equal 500.

Here's one to try on your own.

So, what is the missing number? The sum is 300, one of the parts is 250.

What is the missing part? "What do you add to 250 to equal 300?" asks Sophia.

You can use base 10 blocks to help you if you want, but pause the video and see if you can work out the answer.

And welcome back.

How did you get on? Did you find the missing number? Let's see whether you said the right missing number.

So Andeep says, "I know 50 add 50 equals 100." 5 tens add 5 tens equals 10 tens.

So, 250 add 50 equals 300.

So, the missing part Andeep is saying is 50.

And again, we can represent that using base 10 blocks.

We've got 250 or 2 hundreds and 5 tens, add 5 tens.

5 tens and the 5 tens go together to make 10 tens.

So, the missing part is 50.

Very well done, if you found the missing number Andeep wants to find the missing number.

So, the sum this time is 400 and one of the parts is 260.

Let's represent the 260 using base 10 blocks.

"I know that 260 add 40 equals 300," says Andeep.

So again, Andeep's using known facts to try and help him work out the answer.

Let's add the 40 on and that would add to make 300.

So, 260 add 40 equals 300.

"If I add another 100 the total equals 400," says Sophia.

260 add 140 equals 400.

So, we'd have to add another 100 to get to our sum of 400.

What's been added altogether? We've added 40 and 100.

So, altogether we've added 140.

So, the missing part is 140.

Here's one to try on your own.

So, find the missing number.

So, this time the sum is 300 and one of the parts is 150.

And let's represent the 150 using base 10 blocks.

What do you have to add to 150 to make 300? What is that missing number? Again, you can use base 10 blocks to help you if you want to, but pause the video and see if you can work out the missing number.

And welcome back.

How did you get on? Did you find the missing number? Let's find out if you got the right missing number.

Andeep says "150 add 50 equals 200." So, if we add 50 on, we get our answer 200.

150 Add 150 equals 300.

So, here's 150 add another 150 and that would equal 300.

So, the missing part is 150.

Very well done, if you've got the right answer.

Sophia wants to find the missing number.

So, this time the sum is 300 and one of the parts is 40.

Andeep says, "Use subtraction to calculate the answer." When one of the parts is small, we can subtract it from the sum, subtract it from the whole, and that will give us the other part.

So, here's 300 represented in base 10 blocks, and we're going to subtract 40.

Sophia says, "I know 40 add 60 equals 100." So, we also know 100 subtract 40 equals 60.

So, 300 subtract 40 must equal 260.

So, our missing part is 260.

Again, you can use known facts to help you work out the answers.

Andeep wants to find the missing number.

So, this time the sum is 500 and one of the parts is 30.

"Use subtraction to calculate the answer," says Sophia.

We can represent 500 using base 10 blocks and we can subtract 30, we can subtract 3 tens, and that leaves 7 tens in that last 100.

Andeep says, "I know 30 ad 70 equals 100.

I also know 100 subtract 30 equals 70." So, 500 subtract 30 equals 470.

So, the missing part is 470.

Find the missing number.

So, this is one to try on your own.

So, the sum this time is 400 and one of the parts is 70.

"Use subtraction to calculate the answer," says Andeep.

If you want to represent the sum using base 10 blocks, you can do, I'm gonna start with 400.

How would you find the answer? Pause the video and see if you can work out the missing part.

And again, welcome back.

Did you manage to find that missing part? Let's see whether you got it right.

So, you should subtract 70 from that last 100.

So, 10 tens subtract 7 tens would equal 3 tens or 30.

So, 100 subtract 70 equals 30.

400 subtract 70 equals 330.

So, the missing part is 330.

Very well done, if you've got the right answer.

Sophia solves a bar model problem with three parts.

So, this time you've got the sum being 300 and there are three parts.

300 has been split into one of the parts is 20, another party is 230.

And then there's a final missing part.

We've gotta work out what that part is.

"First I'm going to add 230 and 20, 230 at 20 equals 250," says Sophia.

So, Sophia adds together those two parts to work out what the total of those two parts is.

Andeep says, "250 add 50 equals 300." So, if we add another 50, we get to our sum 300.

So, the missing part is 50.

230 add 20 add 50 equals 300.

When the parts are small, you can use subtraction to find the missing number.

So, in this bar model, the sum, the whole is 400 and two of the parts are 30.

"I'm going to start with 400 and subtract 30 then subtract 30 more," says Sophia.

The number that she's left with will be that missing part.

So, here's 400, let's subtract 30 or 3 tens.

10 tens subtract 3 tens would equal 7 tens or 70.

So, 400 subtract 30 equals 370.

And then Sophia subtracts another 30.

370 subtract 30 equals 340.

400 subtract 30 subtract 30 equals 340.

So, our missing part is 340.

Here's one to try on your own.

Calculate the missing part.

So, this time the sum is 300.

One of the parts is 60, another part is 10.

What is the missing part? And again, if you want to use base 10 blocks to help you represent the numbers, you can do.

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

And welcome back.

Let's see how you got on.

Let's see if you've got the correct missing answer.

So Sophia says, "Start with 300 and subtract 60.

300 subtract 60 equals 240." Then subtract 10 more.

240 subtract 10 equals 230.

So, the missing part is 230.

Very well done, if you've got the right missing number.

That is brilliant.

And let's move on to Task A.

So, in Task A, you've got to find the missing numbers.

You've got the sum and you've got one of the parts.

What is the other part? Can you work out what it is? You can use base 10 blocks or you known facts to help you work out the answers.

Part two of Task A, find the missing numbers.

So, this time there are two parts and you've got to find the missing third part.

What is the missing number? And again, use base 10 blocks and known facts to help you work out the answers.

And then part three of Task A, this bar model has two missing parts.

How many different ways can you use multiples of 10 to make this correct? And again, you can use base 10 blocks and known facts to help you work out the answers.

And this time, there are lots and lots of different answers.

So, pause the video and have a go at Task A.

And welcome back.

And let's look at those answers.

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

So, in that first one, we've got the sum 300.

If one of the parts was 220, the missing part would be 80.

And our second one, if the sum is 300 and one of the parts is 290, the other missing part is 10.

So, very well done, if you completed part one.

Let's have a look at part two.

So, this time you had to find the missing number and there were two parts you were given.

You had to find the third missing part.

So, if that first one, the sum is 400, the whole is 400, one of the parts was 340, another part was 30, the final part was also 30.

So, very well done, if you managed to solve those correctly.

And let's look at the third task.

So, for the third task, here are the possible answers.

So, here are the answers you could have come up with.

So, 400 was a sum in each of them.

So, you could have had the other two parts as being 10 and 80.

300 add 10 add 80 equals 400, or you could have had 20 and 70 as being the two parts.

310 add 20 add 70 also equals 400.

So, very, very well done, if you got onto part three of Task A, and excellent work if you manage to find all the possible answers, that is brilliant.

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

So, the second part of our lesson is using doubles and near doubles of multiples of 10.

Sophia and Andeep double multiples of 10.

So, Andeep says, "10 add 10 equals 20, and 20 add 20 equals 40." So, here's 10 add 10, if we put them together, we double 10, we get 20.

And here's 20 add 20.

If we double 20, we get the answer 40.

Double 20 equals 40.

Sophia says, "30 add 30 equals 60, and 40 and 40 equals 80." So, we take 30 add 30, so double 30, double 30 equals 60.

And then if we do 40 add 40, double 40 equals 80.

Andeep doubles other multiples of 10.

Andeep says, "5 add 5 equals 10." So, 50 add 50 equals 100.

Is 50 add 50, so double 50 equals 100.

6 add 6 equals 12.

So, 60 add 60 equals 120, 6 tens add 6 tens equals 12 tens.

So, double 60 would equal 120.

7 add 7 equals 14.

70 add 70 equals 140.

So, double 70 equals 140.

Calculate these doubles.

So, what is double 80? Here's double 80 represented using base 10 blocks.

What is double 90? And here's 90 add 90 represented as base 10 blocks.

Pause the video and see if you can work out what double 80 is and what double 90 is.

And welcome back.

How did you get on? Did you manage to double both of the numbers? Let's see whether you were right.

So, first of all, let's double 80.

So, 80 doubled is 160.

80 add 80 equals 160.

What's double 90? Well, you might know 9 add 9 or double 9.

And you can use that to help you work out the answer.

So, what is 9 tens add 9 tens? 90 add 90 equals 180.

Double 90 equals 180.

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

Andeep and Sophia calculate 240 add 40.

So, this time we're looking for the missing sum.

One of the parts is 240 and another part is 40.

And we can represent those using base 10 blocks.

So, here we've got 240 add 40.

"I know 40 add 40 equals 80," says Andeep.

"240 is 200 more than 40," says Sophia.

So, that's double the 40.

Let's add the 40 and 40 together, and that equals 80.

240 add 40 equals 280.

So, the missing whole, the missing sum, is 280.

Andeep and Sophia calculate 160 add 60.

Let's represent it as a bar model and as base 10 blocks as well.

"I know 60 at 60 equals 120," says Andeep.

"160 is 100 more than 60, " says Sophia.

So, let's put together the 60 and 60.

60 and 60, or double 60 equals 120.

So, 160 and 60 equals 220.

So, the missing sum is 220.

Andeep and Sophia calculate 270, add 70.

270 and 70 other parts, what's the whole going to be? Let's represent it using base 10 blocks as well.

So, we've got that 270 add 70.

"I know 70 add 70 equals 140," says Andeep.

"270 is 200 more than 70," says Sophia.

So, let's add together that 70 add 70, or double 70, and double 70 equals 140.

So, 270 add 70 equals 340.

So, the missing sum is 340.

Here's one to have it go out on your own.

So, what is 190 add 90? Let's represent it using a bar model and base 10 blocks.

Andeep and Sophia are gonna give you some clues to help you work out the answer.

So, Andeep says, "What is 9 add 9?" How could you use that to help you? Sophia says, "What is 90 add 90?" Pause the video and see if you can work out what 190 add 90 is.

And welcome back.

Let's see whether you've got the right answer.

So, what is 9 add 9? But 9 add 9 is 18.

What's 90 add 90? 90 add 90, double 90 is 180.

So, what is 190 add 90? Let's use our base 10 blocks.

And that will give us the answer, 280.

190 add 90 equals 280.

Very well done, if you've got the correct answer.

Andeep and Sophia calculate 260 add 50 using near doubles.

So, let's represent this problem using a bar model.

And we can also represent the problem using base 10 blocks as well.

"50 add 50 equals 100," says Andeep.

So, 60 add 50 equals 110.

60 is just 10 more than 50.

So, 60 add 50 must equal 110.

Sophia says, "260 is 200 more than 60." So we've got to remember that 200 as well.

So, let's add together the 60 and the 50.

60 and 50 equals 110.

So, 260 and 50 equals 310.

Our missing whole is 310.

Andeep and Sophia calculate 460 add 70 using near doubles.

So, let's represent it using a bar model and let's represent it using base 10 blocks.

Well, quite a lot of base 10 blocks there aren't there? Andeep says, "60 add 60 equals 120." So, 60 add 70 equals 130.

60 add 70 must be 10 more than 60 and 60.

And Sophia says, "460 is 400 more than 60." So, we've got to remember that 400 as well.

Let's add together 60 and 70.

60 add 70 equals 130.

So, 460 add 70 equals 530.

So, the missing sum is 530.

And here's one to try on your own.

What is 280 add 70? Here's a bar model to help you.

And here are some base 10 blocks as well.

And Andeep and Sophia are going to ask you a couple of questions to get you started.

Andeep says, "What is 70 add 70? And how we could use that to help you? Sophia says, "What is 80 add 70?" Pause the video and see if you can add together 280 and 70.

Welcome back.

Did you manage to get the answer? Again, let's see whether you were right.

Let's start off by adding together 80 and 70.

So, 70 add 70 equals 140.

80 add 70 equals 150.

So, let's add together the 80 and the 70 and that gets us the answer 150.

And then all we've got to do is to remember the other 200 as well.

So, the answer would be 350.

280 add 70 equals 350.

Excellent work, if you've got the right answer there.

Let's move on to a couple of problems. Eddie is 270 centimetres tall.

That seems very tall, doesn't it? Oh, it is an elephant.

That's why he's so tall.

He puts on a party hat, which is 60 centimetres tall.

What is the total height of Eddie and his hat? And you might know that elephants are a bit partial to party hats.

They do like wearing party hats.

So, if Eddie puts on a party hat, what is the total height of Eddie and his hat, and how would you work out the answer? We'd have to add together 270 centimetres, that's Eddie's height, and 60 centimetres, that's the height of the hat.

So, 60 add 60 equals 120.

So, 70 and 60 equals 130.

And then 270 is 200 more than 70.

So, 270 centimetres add 60 centimetres equals 330 centimetres.

The total height of Eddie and his hat would be 330 centimetres.

Here's a similar problem to try on your own.

So, Evie is 180 centimetres tall.

There's Evie, Evie's also an elephant.

She puts on a party hat, which is 80 centimetres tall.

What is the total height of Evie and her hat? There's Evie's hat.

She's got quite a tall hat on.

Let's represent the property using a bar model.

So, 180 centimetres, that's Evie's height, add the height of the hat, 80 centimetres, what would be their total height? Pause the video and see if you can work out the answer.

And welcome back.

Did you manage to find the answer? Did you work out the total height of Evie and her hat? Let's see whether you were right.

Here's Andeep with a bit of useful information.

Andeep says, "80 add 80 equals 160." So, we're doubling 80.

"180 is 100 more than 80," says Sophia.

180 centimetres add 80 centimetres equals 260 centimetres.

Excellent work, if you manage to find the correct height of Evie and her hat.

And let's look at Task B.

So, the first part of Task B, you've got to find the missing numbers.

And so, you can use base 10 blocks to help you, or you might have some very useful known facts to help you work out the answers as well.

So, you have to add together the different parts to find the sum.

And here's part two of Task B.

So, calculate the total height of the elephants and their hats.

For the first question, Ezra is 260 centimetres tall and his hat is 60 centimetres tall.

So, complete the bar model and use that to help you work out the total height of Ezra and his hat.

And finally, here is part three of Task B.

So, use any three of these numbers.

You've got there the number 60, 70, 80, 90, 100, 160, 180, and 200.

How many different ways can you complete the bar model? So, the bar model has a total, has a sum of 350.

How can you make any three of those numbers add up to equal 350? See how many different ways you can find the answer.

So, pause the video and have a go at Task B.

And welcome back, and let's look at those answers.

So, let's start off by looking at part one of Task B.

So, if the parts on your bar model were 130 and 30, the sum, the total, the whole would be 160.

If the parts were 170 and 70, the whole would be 240, because 70 add 70 equals 140.

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

So, well done, if you completed part one Task B.

Here are the answers for part two of Task B.

So, Ezra and his hat are 320 centimetres tall.

Ella and her hat are 250 centimetres tall and Emiko and her hat are 270 centimetres tall.

So, what I done if you got onto to part two and you managed to answer those questions as well.

And finally, part three.

So, here are the possible answers.

There are four different ways of finding the answer.

You may have had the parts in a different order, but it counts as the same answer.

So, you could have used 60 add 90 add 200, that equals 350.

You could have used 160 add 90 add 100, that also equals 350.

So, very well done, if you got onto part three of Task B and you managed to find some of those different answers.

Excellent work in your math lesson today.

And I hope you're feeling much more confident at using known facts to help you solve problems by partitioning multiples of 10.

Excellent work today.

Very, very well done indeed.

And let's finish by looking at our lesson summary.

So, use multiples of 10, the total 100, to help you add and subtract with three digit numbers.

Doubles and near doubles can be helpful when adding multiples of 10 together.

And finally, partition 100 into 10 tens and combine tens to make 100 to help you calculate.