# Lesson video

In progress...

I'm Miss Sew and today we are going to be deriving decimal facts.

To start us off.

I've got a math fact for you.

Did you know that every odd number has the letter 'E' inside it? Seven, thirteen, nine, seventeen they all have the letter 'E'.

It's true.

Today we're going to be deriving even more maths facts.

And I hope that we have fun with our learning today.

Make sure that if you have any apps running, you turn off notifications so you can concentrate for the next couple of minutes for your learning.

Today, we are going to be getting ready by warming up with some number bonds.

Next, we're going to start our new learning where we're deriving decimal facts.

After this, we will be using the sentence stem, If I know.

then I know.

to help us understand how we derive decimal facts.

At the end of the lesson, there will be time for you to do some independent learning and also complete the quiz.

Today for our learning, we will need a pencil and some paper.

If you don't have those, pause the video now and go and get them.

And we're going to be doing this super-duper speedily.

This should be really speedy.

Countdown, get your pencil ready, three, pencil and the paper two, one and go! Okay, start to finish your questions if you need extra time pause, and I'm going to show you the answers now.

These were really simple.

I know that you probably did these really quickly.

Now there's a reason why.

And even for these numbers that are a bit greater at the bottom here.

I think you were probably able to do them super speedily.

Pause and mark your work quickly.

Now, why were we able to do all of these answers so speedily including the greater numbers at the end? Let's look why.

Three add four is equal to seven.

This is a known fact, I know this.

With this fact I can use it and apply it to other numbers.

For example, I know that three tens add four tens is equal to seven tens, 30 add 40 is equal to 70.

I know that three hundred add four hundred is equal to seven hundred 300 add 400 is equal to 700.

I also know that three thousand add four thousand is equal to seven thousand.

3000 add 4000 is equal to 7000.

If I know three add four is equal to seven, then I know all of these other facts.

I have derived these facts.

Where I derive facts, I use my existing knowledge, my known facts to help me apply it to other numbers and derive other facts.

If I know.

then I know.

This sentence is going to be really important for our learning today.

Here I have a part part whole model with three ones and four ones.

This represents the equation, three add four is equal to seven.

It also represents the equation, four add three is equal to seven.

Seven subtract four is equal to three.

And the equation seven subtract three is equal to four.

So these are all known facts.

If I know.

we know these facts.

Let's see how I can use these known facts to derive new decimal facts.

I am going to see how these known facts help me with my decimal facts with this part part whole model with 0.

1.

I am looking at tenths.

If I know that three add four is equal to seven, then I know 0.

4 is equal to 0.

7.

If I know that four add three is equal to seven, then I know 0.

3 is equal to 0.

7.

If I know seven, subtract four is equal to three, then I know 0.

7 subtract 0.

4 is equal to 0.

3.

Join in with the last one.

I think we can all do it.

If I know seven, subtract three is equal to four.

Then I know 0.

7 subtract 0.

3 is equal to 0.

4.

I have used my known facts to help me with my derived facts.

I want you to have a go at showing me what you know about your hundreds.

We have done If I know.

together, can you show me what you now know about this part part whole model looking at hundreds.

Okay, let's put the answers down now.

Let's explore this sentence structure.

If I know.

then I know.

a little bit more.

If I know two ones add one more is equal to three.

Then I also know that two tenths add one tenth is equal to three tenths.

0.

1 is equal to 0.

3.

I also know that two hundredths add one hundredth is equal to three hundredths 0.

01 is equal to 0.

03.

And I also know about thousands.

See if you can join in with me.

If I know two add one is equal to three, then I know that two hundredths add one hundredth is equal to three hundredths, 0.

001 is equal to 0.

003.

We can use our known facts to help us derive other decimal facts.

We have done this for our tens, hundreds and thousands in previous maths lessons and you will be able to use this to help you with decimal facts from this lesson onwards.

These answers are all 10 times smaller or I have divided them by 10.

Right.

Time for a quiz.

If I know that five, add three is equal to eight, then I know.

Point to the one that you know.

We know that.

B 0.

3 is equal to 0.

8.

This is 10 times smaller and I have used my known facts to help me apply it to my decimal facts.

Instead of ones, I am using tenths.

Same again, if I know five add three is equal to eight, then I know.

Think carefully and point to the correct answer.

Then I know that.

0.

5 is equal to 0.

8.

Same again, I have gone 10 times smaller, while I'm looking at tenths instead of ones.

If I know five, add three is equal to eight, then I know.

Think carefully, point to the correct answer.

0.

8 subtract 0.

3 is equal to 0.

5.

Let's explore If I know.

then I know.

sentence structure in more detail.

I'm going to use my place value chart to help represent these numbers.

If I know that nine add three is equal to 12, then I know some other facts.

And I know that when I did nine add three, I had tens and ones.

If I know nine add three is equal to 12, then I know 0.

3 is equal to 1.

2.

I regrouped from my tens into my ones and my tenths.

If I know nine add three is equal to 12, then I know 0.

03 is equal to 0.

12.

I have regrouped from my hundreds into my tenths and hundredths.

And finally, if I know nine add three is equal to 12, then I know 0.

003 is equal to 0.

012.

I have regrouped from my thousands into my hundredths and my thousandths.

Time for a quiz.

Think carefully and point to the screen, whether it's A or B.

If I know that 15 subtract six is equal to nine, then I know.

Which of these facts do we know A or B? Then I know.

that 1.

5 subtract 0.

6 is equal to 0.

9.

If I know that 15 subtract six is equal to nine, then I know.

think carefully.

Point to the screen.

Is it A or B? It's A 0.

9 is equal to 1.

5.

If I know 15 minus six is equal to nine, then I know.

Think carefully.

A or B? It is A.

0.

15 subtract 0.

06 is equal to 0.

09.

Some of you might wonder why it's not B.

Let me show you.

Let's have a look why using our place value chart to help us.

0.

15 has one tenth and 0.

6 has got six tenths.

So 0.

6 is the greater number.

When I'm looking at this equation, 15, subtract six, six is a smaller number than 15, 15 is a greater number.

If I applied my known fact to this, it doesn't help me.

Because six tenths is actually more than one tenth.

So it's a different equation and needs a different solution.

What I need is to move this six tenths into our six hundredths.

I can solve this equation if the place value is different, but not if our tenths are larger.

I can solve 0.

15, subtract 0.

06, but not 0.

15, subtract 0.

6.

Now it's time for your independent work.

Have a look at my example, that I will talk through before you have a go yourself.

If I know seven add four is equal to 11, then I know 0.

4 is equal to 1.

1.

0.

04 is equal to 0.

11, 0.

004 is equal to 0.

011.

Let's have a look at the other side.

I'm trying to solve 0.

6, subtract 0.

2 and I know that the known fact that will help me is six subtract two is equal to four.

I can show my answers for what I know.

I've got a challenge for you as well.

What other equations can you derive from your known facts? Think back to earlier in the lesson where I used the part part whole model to show some other facts from these equations.

For example, 1.

1 subtract 0.

7 is equal to 0.

4 or 0.

11 Subtract 0.

04 is equal to 0.

07.

I can use my part part whole to help me understand.

Now it's time for you to get on with your independent work.

Pause the video and go to the worksheet and have a go on your own.