Lesson video

In today's maths, we are going to be subtracting a two digit number and ones with regrouping.

That means we're going to be completing some subtraction equations with regrouping.

Now, this is lesson five of the topic, addition and subtraction.

You will need a paper and pencil.

There are times when you will have to pause the video to have a go at some of the activities yourself.

Now let's get started.

We're going to be looking at the key vocabulary; our star words, creating subtraction sentences using two digit numbers and ones, regrouping when there are more than 10 ones, an independent task and answers, and finally a quiz to see what we remembered.

Here we've got our star words.

Star word, star words.

When I say those star word, I want you to say after me.

My turn first.

Subtract.

Can you show me the sign for subtract? Super.

Subtract.

Dienes.

Group of 10.

Ones.

Make 10.

Regroup.

Super, and we're going to be using this star words today.

But first we need to warm up our brains.

Everybody, let's warm up our brains.

Which of these expressions are equal to or less than 10? How do you know? I want you to have a look at all of the expressions.

Now I want you to pause the video, have a think and then write it down, which of these expressions are equal to or less than 10 and how do you know? That was super quick learning.

Did you get the same as me? Good job.

I love that you were counting in your hands or using your fingers to count.

Some of you used your number bar knowledge.

These expressions are equal to 10 or less than 10.

Excellent work everybody.

Now we are ready to do some subtraction equations with regrouping.

Remember regrouping is when we have more than 10 ones and we need to regroup our numbers to find the right answer to the equation.

So let's have a look.

Here I have another subtraction equation.

Let's say it together.

32 subtract five is equal to? We need to find the answer.

I need to subtract five ones, but 32 only has two ones.

So we cannot take the five ones away from the two ones because there aren't enough ones for us to be able to do that.

This is where our special star word comes in.

We need to regroup.

Can we say we need to regroup? Can you shout it out? I think you can do it louder than that.

Can we say we need to regroup? Super.

I heard you so clearly.

So let's have a look at how we can regroup.

Okay.

So if we can't take the ones, we need to find another strategy.

So one way we could do this is by using our bead string or number line.

If you haven't got one at home, that's fine.

You can use the one on the screen.

Here on our number line, we are going to start at the number 32.

So 32 is our first number in our subtraction equation.

It's also the biggest number, the largest number.

We are going to have my friend, Frodo the frog.

Can everybody say hello? He loves doing jumping, especially on the number line.

Okay, can everybody see him try to wave? Wave at him.

Okay, so now I want everybody to put to the number 32.

So if we start in the number 32, we can see it takes two jumps backwards because we are taking away to get to 30, which is our nearest 10.

But we have only taken away two and we need to take away five.

How many do we need to take away? Five but we've only taken away two.

So we need to continue jumping backwards until we have made five jumps.

This means, if we make another three jumps, we have then jumped backwards five.

What number have we landed on? Shout out your answers out to me.

And then we can see if we are correct.

Can everybody shout out their answers? Oh, I heard lots of correct answers.

If you haven't got it correct, just check again on the number line.

Let's have a look if you've got the same as me.

The answer is 27.

32 take away five is equal to 27.

Good job, let's see if we can do another one.

This time I've got 43, subtract seven is equal to? We need to find out the missing number.

We know we can't take away the seven ones from the three ones so we need to use a different strategy.

Hmm, which one did we use just now? we used our number line.

Let's use our number line again.

Everyone remember, when we're working out subtraction equations, we need to start with the number we are taking away from.

This should always be the biggest or largest number from the equation and that's where we begin our number line.

Can you tell me where we need to start on the number line? Super! The number 43.

So everybody point to the number 43.

and Frodo is going to help us again 'cause he loves jumping.

So we've all got our fingers on the number 43? Okay, so how many jumps will it take to get to the nearest 10? In this equation, the nearest 10 is 40.

So let's jump from 43 all the way to 40.

Are you ready? Go.

One, two, three.

So we've done three jumps from 43 to 40.

Okay, now we need to make more jumps because we are taking away seven, not just three.

So let's carry on counting until we get to seven.

Four, five, six, seven.

Who can tell me what number we have landed on? Can you shout it out? Oh, Frodo the frog can't hear you, can you shout out nice and loud so he can hear you? Super, we've landed on on the number 36.

So 43 takeaway or subtract seven is equal to 36.

Everybody, super-duper working.

Let's see if we can have a look at a different strategy.

This time I've got an equation, but I haven't got a number line.

I have a part-whole model and I've got some dienes.

If the whole is 32, we need to find out what the other part is.

So our equation is 32 subtract five is equal to.

So I've got 32 which is the whole, I've got one of the parts, which is five, but we need to find the other part.

Hmm, what could the other part be? We could use the dienes to help us.

Here we have 32 dienes.

Can you point to the dienes? Let's count.

10 20, 30, 31 32.

So we have 32 dienes but we need to regroup.

What do we need to do? Using 10 of the dienes.

So we need to change them to one group of 10 ones.

Okay so let's change our one 10 to make 10 ones.

Are you ready? Can you help me? So let's get our 10 and change it into 10 ones.

As five, one, two, three, four five, six, seven, eight, nine, 10.

oh, so now we've changed our one 10 into 10 one's.

Let's say it again.

One 10 regroup into 10 ones.

We still have 32 dienes but now we need to move five ones into the parts showing five.

Everybody point to the part showing five.

And now let's move up five ones next to the part that says five.

So let's take our five ones.

Let's move them and everybody help me to move them.

Now we've moved our five ones to the path.

So the ones that we have left and the tens are the other part.

So we can find out what our other part is.

So let's count our other part.

So we've got 10 20, 21, 22, 23, 24, 25, 26, 27.

Our other part is 27.

Great work, everybody.

That means we have 20 17s, which is the other part.

So that also means 32 subtract five is equal to 27.

There we go, so there are two parts; a five and 27.

Great regrouping, everybody.

I loved how we changed our one 10 into ten one so we could regroup and count the other parts.

Great work, everybody.

I think we are ready to do our independent task.

Here we've got lots of different objects.

Ooh, there's a comic with a dog on it.

Ooh, I would like to read that.

They all have different prices on them.

We need to use those to help us in our independent task today.

How much do the children have left? So having a look at the numbers, so we've got 52 pens and the boy, when he buys a pencil.

Having a look at how much the pencil is, then you can do a subtraction equation.

Here is one, just to show you what it might look like.

So here I've got my friend, Sam.

He has 43 pens and he buys an eraser, a rubber, for eight P.

How much money does he have left? So in the whole part module, he has 43 dienes and he changes the one 10 into 10 ones.

So he regroups the one 10 into 10 ones so that he can take away the eight P.

The eight ones for one part.

I've drawn it as well so that you can see.

So let's have a look if you can see this.

So I've drawn my 43.

Here I've got my 43 and then I have my one 10 and I've regrouped.

Can we say, regrouped one 10 into 10 ones.

And I've got my 10 ones here.

And then I put the eight P, the eight ones in one part and the other part I put here to find out my answer.

You might want to do the same.

I did this to help me when I was looking at the subtraction equation so that I get it right.

Also, you can use the dienes and the number line if you need, on this page to help you.

Everybody, I hope you can do some super maths and I'll see you when we do the answers.

Well done.

I like that some of you have used the dienes and some of you have used the number line.

I liked that you wrote it down to find out the answers.

Great work.

Here are the answers.

Have a look.

Here we've got 52 P take away seven P is equal to 45 P.

The second question, 74 P takeaway nine P is equal to 65 P.

The third question, 21 P takeaway six P is equal to 15 P.

I hope you did some great maths.

Super-duper.

I know this was a little bit tricky today with our regrouping, but I liked that everybody worked super, super hard.

Good job.

I hope you had lots and lots of fun today.

I know I did.

Now, I want all of you to complete your end of lesson quiz to see how much you remembered with our subtraction and regrouping.

And now I will see you tomorrow.

Bye.