Lesson video

Hi there, year three.

It's Ms. Hill here.

I'm so excited to be back with you learning.

Today, we're going to be looking at deriving new facts from number bonds, and we're going to be using the phrase, "If I know.

then I know." I can't wait to get started with you today.

So let's get going.

Here we have our lesson agenda.

First, we're going to be using that phrase, "If I know.

then I know." We'll be then moving onto one more, one less.

We're going to practise what we've learned before moving on to the independent task and the quiz.

So, as always, you will need a pencil, a piece of paper, and a ruler.

You'll also need a quiet room free of distractions.

So pause this video in case you need to move or find any of the resources.

Brilliant.

Let's get started.

So here we have our star words! First up, our first word is derive.

My turn, derive.

Your turn.

Our second word is known fact.

My turn, known fact.

Your turn.

Number bond.

Inverse! Place value! Commutative.

Brilliant.

Can you show me derive? Can you show me number bond? Can you show me inverse? And can you show me commutative? Brilliant.

Remember, let's use those star words every time we use our mathematical vocabulary.

Let's get started.

If I know that two add seven is equal to nine, what else do I know? Pause this video and have a think.

Brilliant.

So we know these three facts.

We can have seven add two is equal to nine.

We can have nine subtract two is equal to seven.

And nine subtract seven is equal to two.

This first equation, seven add two is equal to nine, is known as the commutative.

This means that if we move the two and the seven, the answer will always be equal to nine.

For example, seven add two is equal to nine, and two add seven is equal to nine.

These last two sums on the end, these are known as the inversed, so they are the opposite operation.

So the opposite operation of addition is subtraction.

But be careful with the inverse because seven subtract two is not equal to nine.

We need to make sure the greater number is at the beginning of our equation.

So we have the commutative, which means when we move numbers around, the answer will be the same.

And we have the inverse, which is the opposite operation.

Let's explore.

If I know that two add seven is equal to nine, what else do I know? I know one more.

So one more than two is three.

So three add seven is equal to 10.

I could also work out one less.

One less than two is one, so one add seven is equal to eight.

We need to make sure that we balance out the equation.

So we take one less from each side.

We could do the place value so multiples of 10.

For example, two add seven is equal to nine.

Then I also know that 12 add seven is equal to 19.

22 add seven is equal to 29, and 32 add seven is equal to 39.

I just changed the place value of the first number.

I've added a number into the 10s column, which means I also need to make sure I add a 10 into the answer column too for 39.

But here's my favourite.

This one the place value, we can change the 10s for all of the numbers in this equation.

So if I know that two add seven equals to nine, I also know that 20 add 70 is going to be equal to 90.

My turn.

Three add six is equal to nine.

Hmm.

What else do I know? Well, I know that one less, three add five is equal to eight.

I also know one more, three add seven is equal to 10.

I also know that if I change the place value in multiples of 10, that 23 add six is going to be equal to 29.

And then if I want to change the 10s, I know that 30 add 60 is equal to 90.

Hmm.

Pause this video because it's your turn.

If I know that two add eight is equal to 10, ooh, what's one more going to be or one less? The place value where you change the multiples of 10 and the place value when you only change the 10s.

Pause this video and write down your answers.

Great job.

Let's go through those answers together.

So one more, we know that three add eight is equal to 11.

One less, we know one add eight is going to be equal to nine.

Place value, 12 add eight is equal to 20, that's one of our number bonds, 20.

And we know that when we change the 10s, it becomes 20 add 80 is equal to 100.

Great learning! Well done! Let's keep going.

Hmm.

This is going to be our independent task.

Now, five add five is equal to 10.

Now, I know that so I'm going to get my pencil, I'm going to start writing down my answers.

One more, one more than five is equal to six, so six add five is equal to.

Now, I know I need to add one more to my answer, so six add five is equal to 11.

One less, I know five subtract one is equal to four.

So four add five is equal to.

Oh, I need to remember that I need to make sure that I do same thing.

Is equal to nine.

My place value, I'm going to choose 15.

So 15 add five is equal to 20 'cause I need remember I balance it out.

Place value.

Ooh, I'm going do 50 add 50 is equal to 100.

Let's check if I'm correct.

So 15 add five is equal to 20.

And 50 add 50 is equal to 100.

So now it's your turn.

You're going to be doing exactly the same.

Looking at one more, one less, changing the place value 10s, multiples of 10, and then changing the 10s.

I can't wait to see what you produce.

So pause this video, get some nice sharp pencil and write down your answers.

Well done! Let's go through the answers together.

So what I have done is that our one more is in green, one less is in blue.

We'll change the multiples of 10, we've done in purple.

And when we changed the 10s place, I've done in pink.

So once I put up all of the answers, pause the video and tick and fix, Pause the video.

If you'd like to, please ask your parents or carer to share your work on Twitter, tagging @OakNational and #LearnwithOak.

I really enjoyed learning with you today, and I hope you have as well.

And I look forward to learning with you another day.

So before you go, complete the quiz.

Good luck and see you soon.