Lesson video

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

We're going to be carrying on our unit, which is exploring calculation strategies, and today's session, our objective will be to consolidate our learning and to apply our learning.

So let's get started.

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

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

Well, let's start today with the little riddle.

Where can you find cities, towns, shops and streets, but no people? Where can you find cities, towns, shops and streets, but no people? Have a think.

You can find it on a map, but until those of you who guessed that correctly, let's get started ourselves started, then.

As I said, our agenda for the lesson today is going to be to consolidate and apply knowledge of calculation strategies.

I'm going to be showing you a series of different questions and I'll get you to be time to pause as we go through for you to answer the questions.

So there's no quizzes today.

So after this question, then, what's the same and what's different.

Our equation is 43.

Plus 25 is equal to 68.

I'm going to give you about 10 seconds.

Have a look, really closely, at the different images that you can see on the screen and consider the question.

What's the same and what's different.

Then we'll discuss it together.

You can jot some things down, but you don't have to.

Pause the screen now to have a go at this question.

Welcome back.

Okay, let's have a look, then.

What's the same and what's different? Now, I can see my equations here.

I can say it's represented in three different ways.

So it's represented here.

I'm number line.

So I've got 43 plus 20 plus five, so it's been partitioned.

I can see here, it's written with numbers and our place value grid.

And I can see here, it's going to return to that used, it's been represented survey using Dienes and our face value grid, but it's the same numbers on the same equation, represented in three different ways.

Have a look at our next question, then.

Next, I would like you to have a go at calculating the addition and subtraction equations that are shown on the screen.

We've got four equations here.

So I'd like you to pause the screen now to have a got these, we'll go through the answers together at the end.

You'll need your paper for this activity.

So please pause the screen now, and have a go at these equations.

Let's have a look, then, at the answers.

So we're going to start with this equation over here, 51 plus 23, I always start with my one's column.

One plus three is equal to four.

My 10s column five tens plus two 10s is equal to seven 10s.

So my answer is 74.

Next equation, then.

38 plus the 17.

I again have to start with my one's column.

Eight plus seven is equal to 15.

This time I've had to regroup because I've got 10 and 15, sorry, I've got 10 ones and five ones.

So I partitioned it into one group of 10 and I've put them here.

Now I can do three and one is four, add one, it's five.

So my answer is 55.

Now I'm looking, and I need to make sure I'm subtracting this right.

Really important, we look at the operation that the equation is asking from us.

So again, I start with my ones.

This time I'm doing six subtract three, is going to give me three.

And then I need to do four subtract two, to equal the two.

I know that that two represents two 10s because it's in my 10s column, then my answer is 23.

And lastly, I've got 87 subtract 39.

Now, when I'm looking at this, I know that this number that I want to subtract is greater than the number I want to subtract it from because nine is greater than seven.

So I have to do some regrouping.

So eight 10s become seven 10s and 10 ones.

Now I have 17 subtract nine, which I can do to, which is equal to eight.

Seven take away three, which is equal to four.

I know that four really represents four 10s because it's in my 10s column.

Then my answer is 48.

Well done you two, let's have a look at the next thing we're going to look at today, then.

This time, I would like you to have a look and see if you can spot the mistake.

Our equation is 46 plus 25 is equal to 61, somewhere I've gone wrong.

Can you help me? Can you see where I've gone wrong.

Pause the screen now to have a look at where you think I've gone wrong, we'll have a look at it together in about 10 seconds time.

Okay.

Let's have a look then.

So I know I always start with my ones.

I've got 46 partitioned here, 25 partitioned here.

That's fine.

Six plus five is equal to 11.

You can see here, I've regrouped my one 10 and my one here, this column is correct.

Now I have to add my tens.

I've done four and two as equal to six.

I've forgotten to add my regroups one.

So my answer here, shouldn't be a six.

It should be a seven.

Well done to those of you that spotted that I've forgotten to add a number that I've regrouped here.

''cause in total, I have seven ones, so my answer should have been 71.

Next, then.

I'd let you to have a go at matching the equations with the correct answers.

Look really carefully at what those equations are because some of them look similar, so you need to look at the operation and the numbers before you link them.

You might want to jot this down on your paper.

Pause the screen now to have a go at this question, we'll go through the answer in a moment.

Okay then, let's start with our first one.

64, subtract two.

I know I'm subtracting, and I'm only subtracting two.

So I know if I look down here, my answer would be 62.

Next one.

64 plus 20, so add 20.

So I'm looking this time at my 10s column and I'm adding 20.

I know that 64 add 20 would give me 84.

This time it's 64 subtract 20.

So it was really important that we look at our operation.

64 subtract 20 is going to give me 44, 'cause I'm subtracting 20 from my 10s.

And my last one is 64 plus two.

I know that 64 plus two is 66.

Well done to those of you who got that right.

That was a bit tricky because you had to look really carefully at those operations and those numbers.

This time, I'd like you to have a look.

What's the same and what's different about the equation here and how it's represented here.

You don't need to do anything, Dan.

You just need to have a good look at the screen.

So pause the video now for 10 seconds, and then we'll go through it together.

Okay.

Let's see, then.

Our equation was 68 subtract 25 is equal to 43.

Now you can see this has been represented in three different ways.

Here we've got our number line with 68 on it.

We've partitioned 25 into 20 and five and shown our answer, here, as 43.

Just like it is here.

This time, it's been shown with written numbers and a place value grid.

We've subtracted again.

Give us that answer.

And this time here it's been represented in our place value grid, but with Dienes.

Next, then.

I would like you to have a go at this question.

Take the correct bar model to match the problem below.

So you've got two bar models here.

Your problem: Laura and Abdul are creating a banner using string.

Laura has 62 centimetres of string.

Abdul has 34 centimetres more string than Laura.

How much string does Abdul have? So you need have a look here at the two bar models and think about which bar model represents this question.

And then as my challenge to you today, I'd like you to actually solve the problem and work out how much string Abdul has.

Already got centimetres written down.

So this time, you will need to pause it and you will need to do some working out on your paper.

So pause the screen now, and we'll go through the answer in a moment.

Okay, welcome back.

Firstly, we're going to look up which bar model matches.

So, Laura had 62 centimetres of string.

Abdul has 34 centimetres more string than Laura.

So if we look at this bar model, we know Laura has 62 centimetres, right? And we know Abdul has 34 centimetres more.

We want to know that total amount.

And this is the bar models that matches with our question.

Now to solve that equation, we need to do some addition.

We need to do 62 add 34.

And it's going to give us 96 centimetres of string.

So Abdul has 96 centimetres of string.

Well done to those of you who worked out both parts of that.

Let's have a look then at the next problem.

What I'd like you to do now is identify the missing numbers in the equations and show your working out.

So you've got two equations here, have a look really carefully at them and what you're going to do to solve those equations.

Pause the video now.

And then we'll go through the answers in a moment.

Welcome back.

Let's have a look, then, at equation A.

We had 82 subtract something is equal to 29.

Now to work that out, we need to know what this missing number is here.

So we need to find out the difference between 82 and 29 by subtracting 29 away from 82 to give us this number.

The answer was 53.

For B, we had 27 plus something is equal to 82.

This time, I need to work out what that number is.

So I need to do 82 subtract 27, and it's going to give me 55 to give me that missing number.

Next then.

I would like you to spot the mistake.

You've got 61 subtract 25 is equal to 46.

I've gone wrong somewhere and I need your help.

This time, you don't need to make any notes.

So just have a look at the screen when it's paused and see where I've gone wrong to help me out.

Pause the screen now to help me out.

Okay.

Let's have a look.

Well done to those of you that have noticed.

I've partitioned 61 into six 10s and one one.

And 25 into two 10s and five ones.

Next I've seen that one here.

I cannot subtract five from it.

So I needed to regroup one group of 10 to 10 ones.

Now I've put my 10 ones here.

What have I forgotten to do with my 10s column here? That's right.

I've forgotten to regroup it because there's actually now only five 10s remaining because I regrouped one of those 10s for 10 ones.

So my answer in my 10s column cannot be correct, because I've got one group of 10s, too many remaining over here.

So my answer should be, fixing the ones column, but I should have five subtract two.

Then my answer should be 36, not 46.

Well done to those of you who got that correct.

Next question, then.

I'd like you to have it out.

Identifying the missing numbers in the equations.

Have a look really closely at the equations.

Have a look at the operation in the equations before you answer them.

You'll need to make some notes and some jottings down on your paper for this question.

So please pause the screen now to have a go this question.

Well done for your really hard work today, let's have a look, then, at these.

We're going to look at them one equation at a time.

So 57 plus something is equal to 60.

I know that 57 plus three is equal to 60.

Next, then.

I've got 40 is equal to 56, subtract a number.

That number was 16 is going to give me 40.

Now I've got something plus four is 50.

Well, I know that if I take four away from 50, it would give me 46.

So my missing number must be 46.

70 is equal to something add 63.

I know that 63 plus seven is equal to 70.

Now I'd like you to have a go at answering this question here.

Calculate the answer to the question below.

Remember to show your method.

Your equation is 54 plus 38.

And once you've shown your method once, I want you to have a go showing it in a different way, just like we've seen in the previous equations before.

See if you can solve it using two different methods.

You'll have a look at the answer afterwards.

Pause the screen now to have a go at answering this equation.

Okay, let's have a look, then, what the answer is.

The answer is 92.

You could have solved that drawing Dienes.

You could have solved that with using the expanded method, or using the column method, or you could have done some rounding and adjusting with 38 and counting on your 10s.

There are different ways you could have solved it.

You could have even used a number line to solve that.

So well done for working really hard and showing more than one way of solving an equation.

You've worked really, really hard today, on lots of different questions.

Well done for working so hard today.

It is the last session of this unit.

Thank you for all of your hard work for the last few lessons and I'll see you again soon.

Bye bye!.