# Lesson video

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I'm Mrs. Crane, and welcome to today's lesson.

For today's session, we're going to be exploring calculation strategies, and we're going to be looking at adding two, 2-digit numbers together when they require regrouping by using the column method today.

For this lesson, you will need a pencil and some paper.

Please pause the video now to go and get these things if you haven't got them already.

So, today I thought we could start with a dog fact.

Did you know, a greyhound could beat a cheetah in a long distance running race? That mean that I didn't know either.

Let's get started and see what we're up to today.

So, our agenda for today's lesson.

We're going to be learning how to use the column method for adding two 2-digit numbers that require regrouping together.

We're going to start with a quiz, to test your knowledge, then we're going to look at some star words for today.

We're going to find out how we use the column method, when we need to regroup a 10, then it will be time for your talk task.

After that, we will develop our learning for when we need to regroup a number that's greater than 10, then it will be time for you to do your independent task and we'll review the answers together.

And finally, there'll be a quiz to see what you've remembered.

Please pause the video now to complete your starter quiz.

Welcome back.

Let's get started then with today's star words or do my turn your turn.

Place value, tens, ones, add, column, is equal to, regroup.

Well done Year 2, brilliant.

Let's have a look then, at our New Learning today.

So, we've got our equation here.

We've got 17 plus 33.

Let's have a think then.

I'm going to show you first with dienes here with pictures of dienes, then we'll look at how we do it with written numbers afterwards, okay? So, I'm going to start with my tens.

How do I do that? Let's try it and see what happens.

So, I have one 10 here, because I've partitioned 17 into one 10, and seven ones.

And I have three tens here, because I've partitioned 33 into three tens and three ones.

Let's have a go then.

My one 10 plus my four tens, my three tens, sorry, is going to give me that's right, four tens.

Here we go.

One, two, three, four tens.

Let's have a look then.

I want my seven ones, seven here, eight, nine, 10 ones.

Put them here.

Oh, can you spot what's happened? Something's gone wrong somewhere.

Well done to those of you that noticed.

I can't put 10 ones in my ones' column.

So I need to start with a different column.

I can't start with my tens' column, because it doesn't work.

But let's get rid of those dienes and start again.

So this time, I'm going to start with my ones' column.

I know I've got seven ones here, let's count them altogether, count with me.

One, two, three, four, five, six, seven, plus three, seven, eight, nine, ten.

We just did it, let's see.

There we go, we've got our 10 dienes here.

Now this time, I need to do something very different with my 10 ones.

I need to do something called regrouping them.

And I need to regroup one group of 10 ones to one 10.

So let's regroup that and make one tens diene.

Now, can that tens diene stay in that ones' column? What do you think? Have a little think.

Well done to those of you that says no it can't, because now I've got 10 ones the same as saying, one group of 10, so I need to regroup it and move it into my tens' column.

So I'm going to put it here, so that when I count my tens, I don't forget it, it's over here, I'm going to forget it, and it's not going to help me get the right number.

That's my answer.

So, let's now look at our tens' column because we've done our ones' column.

We've got one 10 here, two tens, three tens, four tens, five tens.

Let's put our five tens in here.

Five tens is the same as saying 50.

Well done to those of you who were working that out with me and counting along with me.

Now, what we're going to do is have a look at what happens when we write it down with written numbers.

Let's do them.

So again, just like I had here, I've partitioned 17 into one 10 and seven ones.

I've just written them rather than drawn them.

And I've partitioned 33 into three tens and three ones.

So I've partitioned them exactly the same.

I'm going to show you now what happened when I added my tens first.

So let's have a look.

One plus three is four.

So, I've got my four tens here.

Let's have a look then at what happens when I add my ones next.

Seven plus three equals 10.

Oh dear, you can see really clearly here, this can't be right.

My number can't be four 10 or 410, because that's not right, because my four should be in my tens' column.

So that shows exactly why we have to start with our ones first.

So let's get rid of those two numbers, bye-bye, and start so fresh with our ones' column.

So, seven plus three is equal to 10.

This time, you'll notice I've written it slightly differently.

I've put my zero here as a placeholder.

I need to know there are zero ones in 10, because there are 10 ones, so there's one group of 10.

So I'm going to put my one here, because it represents one group of 10.

Now, I can add them up.

I can do one plus three is four plus one is equal to five.

Five tens shows 50, exactly the same as here, but it looks slightly different.

Let's have a look then, at another example.

This time our number is 38 plus 22.

I want you to have a think.

Will my equation require regrouping? If you think it does, how do you know? We're going to come back to that at the end of our example, to find out if you're correct or not.

So, I know I have to start with my ones' column.

We've worked that out from my previous example.

So, I've partitioned 38 into three tens and eight ones.

And I've partitioned 22 into two tens and two ones.

So the first thing that I have to do, is add my ones' column, I need to do my eight plus my two.

So I'm going to count them, one, two, three, four, five, six, seven, eight, nine, 10.

And I've regrouped that 10, I'm sorry, I've put them altogether here, the 10 ones.

The next thing I have to do is regroup my 10 ones for one 10.

Let's regroup it for one 10.

And let's put it in the correct place, because we know that our one 10 can't go in our ones' column, because it represents a 10.

So let's put it there ready in our tens' column.

There it is.

Now, let's count our tens.

You can count along with me.

I'm going to count our tens.

One, two, three, four, five, six tens, which is the same as saying 60.

Let's put them where they belong, here's our six tens.

Let's double-check, one, two, three, four, five, six.

We've got our six tens, that shows me that that it's 60.

Now let's have a look at what happens when we use our written numbers rather than our dienes.

Here we go, we've got 38, again, partitioned into three tens and eight ones, and 22 partitioned into two tens and two ones.

Again, we're going to start with ones' column.

And well done to those of you that have remembered that eight plus two is equal to 10.

What do I need to do to make that 10 look correct? Have a think.

Well done to those of you who've told me and have said, you need to regroup your 10 and show it with one 10 in the tens column and a zero as a place holder.

Let's do that now.

Perfect, that's much better.

Now I can ask three, add two which is five, add one is six.

I know that six represents six tens, because it's my tens' column.

So again, it shows 60.

Let's go back to that original question then.

Did I need to regroup? Yes, I did.

Why did I need to regroup? How did you know? I needed to regroup because the numbers in my ones' column were number bonds to 10.

So, as soon as those numbers in my ones' column, if I look carefully here, our number bond to 10, I know that I need to regroup.

If it is a number bond that makes more than 10, we're going to look at those equations after our talk today.

So let's have a look at what your talk task is.

Today's talk task.

Using dienes, pictures of dienes or numbers, complete the following equations.

I'm going to show you quickly what I mean about pictures of dienes.

So what I've done so that you can see what a picture of diene might look like, if you're drawing it at home, is I've just drawn out a dienes grid.

I've done the tens here, the ones here, and I've drawn out my tens dienes and my ones dienes.

It don't have to be a really complicated drawing, it can just be something quick and just drawn really quickly so that it shows if you want to, what a 10 looks like, and what a one looks like.

Hopefully that should help you.

So, you've got 25 plus 15 and 12 plus 18.

You've got a blank grid there that you can use to help you draw out your own one if you'd like to.

Today's say it out loud is here, I'll read it out to you before you pause your screen.

This number has tens and ones, and this number has tens and ones.

Ones add ones is equal to.

I will regroup 10 ones for one 10.

Tens add tens is equal to.

Pause the video now to have a go at today's talk task.

Welcome back Year 2.

Let's have a look then at today's Develop Learning.

My equation says 38 plus 23 is equal to.

I've got two questions.

Let's have a look at Question 1 first.

Should we add the tens or the ones first? You're going to have five seconds thinking time, and then we'll answer that question together.

Well done to those of you that have remembered we must add the ones first, otherwise, we get ourselves a bit stuck and confused when we come to regrouping and our columns don't work out correctly.

So we're going to always ask our ones first.

Next question.

Will our equation involve regrouping? Why or why not? Five seconds thinking time.

Okay, well done to those of you who said, yes, it will involve regrouping.

Why? Let's think about what we just talked about.

Look at our ones' column.

Eight plus three.

Eight add three I know makes a 11, that's greater than 10.

And I know that if makes 10 or more, I have to regroup.

So I'm always looking for these numbers here.

If they're a number bond of 10, they definitely have to be regrouped.

If they're a number bond of more than 10, if the sum of those two numbers is more than 10, then I know I have to regroup.

So, let's have a look then at how we can solve this equation.

So, we've partitioned 38 into three tens, one, two, three, and eight ones, one, two, three, four, five, six, seven, eight.

We partitioned 23 into two tens, and one, two, three.

Then we must start with our ones.

So, we're going to do eight ones add three ones.

So, we've got eight, nine, 10, 11.

Let's see, we've got 11 dienes here.

Let's count them to check.

One, two, three, four, five, six, seven, eight, nine, 10, 11.

Got 11 ones here.

Now I need to do something very similar to what we did before, but there's a slight difference.

So this time we have to regroup our 11 for one 10, because there's one 10 in 11, and one one, because there is one one in 11.

So, this represents here, the 11.

You can imagine that here as 11.

Now, I've done the ones' column.

Well done to those of you who are saying yes miss, you must do the tens' column next.

So let's look.

We now have one, two, three, four, five, six tens, which is the same as saying 60, but we need to put six tens in our tens' column.

Here we go.

One, two, three, four, five, six.

So our answer is 61.

Let's have a look then at what's happening behind here and numbers that are written down this time, not just adding.

So, I've got 38, again, partitioned into three tens and eight ones.

And I've got 23 partitioned into two tens and three ones.

I must start with my ones.

Eight add three is equal to 11.

Again, shown here, there's one 10 in 11, there's one one in 11.

You can see the same here shown on our dienes as being shown here by our numbers.

Now we're going to have a go at adding our tens' column.

Three plus two is five, plus one is six.

I know that six represents six tens, in my tens' column.

So my answer is 61.

The same as here.

Okay, you're now ready for today's independent task.

Today's independent task.

I would like you to solve the following equations using dienes, pictures of dienes, or the column method.

You've got six different equations here.

Remember, always start with the ones' column.

Please pause the video now to complete your task.

Okay, welcome back.

Let's have a look at today's answers then.

So, we're going to start with this question here.

We're going to do eight plus six is equal to 14, put my one in my tens' column, four in my ones' column.

Four plus three plus one is equal to eight.

So my answer is 84.

Next question.

Six plus seven is 13.

So, I put my three to represent the three ones here, and my one to represent my one 10 here.

Three plus four is seven, plus one is equal to eight.

Next then, eight add seven equals 15.

Then I need to do four plus three plus one which is equal to eight.

So my answer is 85.

Well, look down here then.

Eight plus eight is 16.

So I share it here, my one here, to represent one 10.

My six here represents six ones, four plus three plus one is equal to eight.

So my answer is 86.

Here we've got 36 add 45, six plus five is equal to 11.

So I put my one here to represent one 10, my one here to represent one one.

Three plus four plus one is equal to eight.

So my answer is 81.

Last one then.

Six plus six is equal to 12.

So, I put my one here, my two here.

I then do three plus four plus one which is equal to eight, to give me 82.

Well done for working so hard today.

Please pause the video now to complete the final quiz and answer a few questions.

See you again soon, bye.