Lesson video

Hello everybody and welcome back to another math lesson with me, Mrs. Popel.

As always, I'm hoping that we're gonna learn lots of new things and have lots of fun, so let's get started.

This lesson is called Use Known Additional Subtraction Facts Within 10 to solve problems, and it comes from the unit secure fluency of addition and subtraction facts within 10.

By the end of this lesson, you should be able to use known addition and subtraction facts within 10 to help you to solve problems. Let's have a look at this lesson's keywords, strategy.

Just the one today, my turn strategy, your turn.

Well done.

Let's have a look at the lesson outline.

So in the first part of our learning, we are going to be identifying the best strategy to use to help us solve a problem, and in the second part, we are going to use a range of strategies to solve a range of problems. Let's get started with the first part, identifying the best strategy to use to solve a problem.

In this lesson, you are going to meet Izzy and Alex.

They're going to help us with our learning today.

Izzy and Alex are practising all the strategies that they have learned so far.

They have a set of addition and subtraction, fact cards.

They turn over one of the equations and discuss what the best strategy will be to find the sum or the difference.

Alex turns over the first card nine, subtract one is equal to.

Hmm.

What do we think the best strategy is going to be to help us solve this problem? Alex can see that we are subtracting one, so he thinks the best strategy to use is thinking of this as one less, one less than nine is the number before in our count.

So that is eight, nine minus one must be equal to eight.

Well done Alex and Izzy.

Izzy now turns over another card.

Three plus two is equal to something.

Hmm? What method are you going to use, Izzy? Izzy can see that we're adding two to an odd number because three is an odd number, so we can see this as the next odd number in our account.

Alex sees this a little bit differently.

He sees this as a near double because the two add-ins have a difference of one.

Hmm.

They decide to both use their own strategies to see if they get the same number.

The odd number after three is five.

So Izzy thinks that three plus two is equal to five.

Oh, let's see what Alex gets.

Three is one more than two so he can double two, which is and add one more, which is five.

Ooh, both of them have got five as their sum, so three plus two must be equal to five.

Well done guys.

The children turnover one more card.

Four plus four is equal to? Double.

They both notice that this is a double.

They know that four plus four is the same as double four and they know that double four is eight.

Alex also knew that double four was eight, but he did it a little bit differently.

He pictured it on his number frame in his head.

Four and four is eight.

Well done to both of you.

You both got that one.

Okay, then over to you, let's have a go at a similar game to Alex and Izzy's.

I'm going to show you an equation and what I would like you to do is to think about which strategy would be best to solve that problem and we are going to pop it into the correct column.

Here you can see we have a table filled with all the strategies that we have used so far in our learning.

Double near double.

One more, one less next, odd or even number and odd or even number before.

I'm going to show you an equation that hasn't been solved yet and I'd like you to think simply what strategy would I use to help me to solve this? I will ask you to pause after each equation to have a think before you then press play to find out which would be the correct strategy.

Let's have a go.

Four plus two, have a pause with this video and come on back when you're ready to see if you put it in the same column as me.

I can see that four is an even number and when we add two to an even number, we can see this as the next even number.

So we would use that strategy to help us.

Well done if you've got that one.

Here's your next one, three plus one.

Pause the video and have a think.

Which strategy would be best? Okay, three plus one.

We can see that we are adding one and when we add one, we can think of this as one more.

So we would use the one more strategy to solve this, one more than three.

10 subtract two.

Pause this video again and have a little think if you need a little bit more time.

Okay, 10 is an even number and when we subtract two we can see this as the odd or even number before.

So because 10 is an even number 10, subtract two would be seen as the even number before.

So I'm going to put that in that column.

Well done if you've got that one, two plus three.

Pause this video and have a think which strategy would help you to solve two plus three.

Okay, then two plus three.

Hmm, let's have a look.

Two plus three.

Oh, Alex has noticed that this might be solved using two different strategies.

He says that we could use a near double yes, Alex, because two and three have a difference of one.

So we could use our near double to help us, but also I didn't notice that Alex.

Well done.

We could use see this as the next odd number strategy because three is an odd number and we're adding two.

So we could simply see this as the next odd number.

Two plus three or three plus two.

Well done Alex.

So we could have put two plus three in either of those columns.

Well done if you've got one of those and the super well done if you've got both of them.

Next one, nine, subtract one.

Hmm, pause this video and have a think which strategy would you use? Okay, we can see nine is an odd number.

Hmm but I'm subtracting one and I know when I subtract one I can simply see this as one less.

So I would put that in that column.

Well done if you spotted that one.

And finally two plus two.

A nice easy one there.

Pause this video if you need a little bit more thinking time, two plus two.

We know that two equal add ends being added together is the same as doubling.

So we could say double two.

Well done if you've got all of those, let's have a look at what task A is for this lesson.

Task A.

You will need a set of equation cards and a strategy table.

Turn over an equation card and match it with the strategy that you are going to use to find the sum or the difference.

Then use that strategy to solve the problem.

Pause this video and have a practise and have a play of this game and come on back when you're ready to continue with the lesson.

Welcome back.

I hope you enjoy playing that game.

Let's see how Alex got on.

So Alex, what's your first card? Four plus one is equal to something.

Hmm.

Alex, where are you gonna put this? We can see plus one as one more, so he puts this into that column.

Now let's solve it.

Alex, one more than four is five.

So four plus one must be equal to five.

Well done, Alex.

Which one did you turn over next? Five plus four.

Hmm.

What strategy are you going to use, Alex? He can use double five to help him solve this.

So he's going to put that into the near double category.

Double five is one more than four plus five.

One less than 10 is nine.

So five plus four is equal to nine.

Well done Alex.

Some super use of your knowledge there.

Let's have a look at the second part of our learning.

We are going to use a range of strategies to solve problems. So let's get started.

Alex now challenges Izzy to play his new game.

He says that they need to select two digit cards and then an operation card to create an equation for them to solve using their strategies.

Izzy has a turn, she turns over a three and a seven.

What operation is she going to select? Ooh, subtract.

She then lays the cards down to create her equation.

Seven subtract three and she needs one more card.

What does she need? It equals fantastic, 'cause that means she's going to solve it.

So seven subtract three is equal to something.

She now thinks about the best strategy to find the difference between seven and three.

She's not sure what strategy to use, so she's going to use a bar model to help her represent the problem.

She knows that seven is the whole and three is a part.

The missing part will be the difference.

So how are you going to work this out then Izzy? She's going to think about what she knows.

She knows that double three is six and this hole is one more, so we can use that near double knowledge to help us to solve this.

Three plus three is equal to six, but my hole is seven.

So what does that mean for our missing addend? We can see this as one more, so the missing part must be one more than three.

So that means the missing part must be four.

Izzy is explaining that if she knows that three plus four is equal to seven, then she knows that seven subtract three must be equal to four.

Well done Izzy, I love how you've used lots of your prior learning to help you to solve that.

You use your near doubles, but also the relationship between addition and subtraction to help you find that missing part.

Well done.

Alex now selects his cards oh, eight subtract two is equal to? How are you gonna solve this one then Alex? Alex thinks about the best strategy to find the difference.

He knows that eight is an even number, so subtracting two from an even number will give him the even number before.

So eight, subtract two must be equal to six.

We can see that this is the even number before eight.

So eight subtract two must be equal to six.

Well done Alex.

It's now Izzy's turn again.

Let's see what she gets this time.

A one, a four, and which operation are you going to choose Izzy? Addition.

Hmm, let's put those cards down then.

Four plus one.

Oh, what does Izzy forgotten? She's forgotten her equals card.

Let's pop it in now then quick, Izzy, there we go.

Okay then Izzy, what's going to be the best strategy to help you to solve this problem? We can see adding one as one more and we know that one more than four, is five.

So four plus one must be equal to five.

Well done Izzy.

Okay, then over to you.

So you can see that we have got three equations that need solving and three strategies that the children have used to solve them.

Your first job is to match up the equation with the strategy that the children use to solve it.

Then could you use that strategy to then solve the problem, pause this video and have a go and come on back when you're ready to find out how you got on.

Welcome back.

Let's have a look at which strategies would help us to solve which equations.

So two plus six.

Hmm, I know that six and two are both even numbers, so it can't be the odd number before.

I know that one more is adding one and this is adding two.

So this must be the next even number and I know that when we add two to an even number, it is the next even number.

So let's join that up.

Well done Alex.

Six is an even number and I remember that we can add two in any order and see this as the next even number, six plus two is equal to eight.

Well done if you've got that correct and spotted that that was the strategy to solve it, three plus one.

Let's have a look, Alex, what are you thinking? Adding one can be seen as one more.

One more than three is four, so three plus one is equal to four.

Well done, if you've got that one, now I've got one strategy left.

I wonder which one it could be.

We know that nine minus two is the same as the odd number before, so what is the odd number before Alex? The odd number before nine is seven, so nine minus two must be equal to seven.

Well done to Alex and well done to you if you've got those correct too.

Okay, then let's practise all this wonderful learning with task B.

For task B, you're going to need a board game, two coloured counters and some strategy cards.

You're going to turn over a strategy card and find an equation on the board that can be solved using that strategy.

Izzy gonna show us how this is done.

She turns over her strategy card and it says one less.

She finds an equation that can be solved using one less nine minus one.

Well done Izzy, she then solves this problem.

If she's correct, she can cover the equation with her coloured counter.

If she's incorrect, she gives it over to her partner who has a chance to steal it and put their counter if they're correct, we can see subtracting one as one less, one less than nine is eight, so nine minus one is equal to eight.

Is is Izzy correct? Yes.

Well done Izzy.

So Izzy gets to put her counter over the top of that equation.

Once all the equations are covered on the board, the winner is the person with the most counters.

Pause this video and have a play of this game with your partner.

Don't worry if you haven't got a partner, you can play this game on your own and just challenge yourself to get as many correct as you can.

Come on back once you're ready to continue with the learning.

Welcome back.

I hope you enjoy playing Task B.

Let's see how the rest of Alex and Izzy's game went on.

It's now Alex's turn.

He turns over a double.

Hmm.

Can you see a double on the board, Alex? Alex knows that double is adding two equal add-ins.

So five plus five is a double.

He knows that double five is 10.

Is he correct? Yes, he is.

Well done Alex.

That is your counter.

Now it's Izzy's turn again.

Oh, an odd number before which equation on this board can be solved using the odd number before strategy? Seven minus two.

The odd number before is two less than an odd number and seven is an odd number.

Two less than seven is five.

Izzy is correct, so she gets to put her counter on the board.

Well done Izzy.

Alex's turn again, oh, adding zero oh.

Can you see an adding zero on the board, Alex? It's there.

Well done.

One plus zero.

What can you remember about adding zero, Alex? Adding zero does not change the number, so one plus zero is equal to one.

Well done Alex, you get to put your counter on the board.

We'll let Alex and Izzy continue with their game.

While we have a look at what we have learned today, we can use a range of strategies to solve problems within 10.

We can use our knowledge of doubles to solve near double problems. When we add and subtract one, we can see this as one more or one less.

When we find two more than an odd or even number, we can see this as the odd or even number after in our count.

When we find two less than an odd or an even number, we can see this as the odd or even number before in our count.

I hope you've enjoyed playing all of the games to help you with your learning.

Remember, these games can be played at any time.

It doesn't just have to be in this lesson.

Thank you for sharing your learning with me today and I hope to see you again soon.

Goodbye.