# Lesson video

In progress...

Hello, my name is Miss Robson.

In this lesson, we are going to be exploring further problems involving addition and subtraction.

We have to start today by learning about Leah's number line.

We're then going to complete a talk task, doing an activity that she likes to do on her number line.

Then we're going to look Tom's number line.

This lesson is all about a game that two children, Tom and Leah play.

It's called secret jumps.

We're going to first learn about how Leah plays the game.

Leah always has a number line that looks like the one on the screen and a counter.

I'm going to be using my pointer.

She always starts with her counter at zero.

So I'm starting with my pointer at zero.

Leah's number line, goes from left to right and looks just like this.

Leah made a jump of three along her number line, and then a jumper four.

Where did she land? So she started at zero.

She made a jump of three.

Then she made a jump of four.

Let's have a go at that together.

Count with me.

First, we need to count on three, ready? One, two, three.

We've landed at the number three.

Next we need to count on four.

So one, two, three, four.

Now we've landed on the number seven.

So the question is where did she land? And we know that she has landed on the number seven.

The next question says, Leah made a jump of four along her number line and then a jump of two.

Where did she land? So we need to start at zero again.

This time she's making a jump of four, then a jump of two.

Pause the video here, and using your finger on the number line on the screen, jump along the number line four jumps, and then two jumps.

And see if you can figure out where she landed.

Leah would have jumped four first.

One, two, three, four.

So she landed at four.

And then she made a jump of two.

One, two, she's landed on the number six.

Now, Tom and Leah used to play this game with each other a lot.

But it was too easy when they gave away what both of their jumps were.

It's quite easy for us to work out what the number is, isn't it? We jump on four and then we jump on two.

Or with the last one we jumped on the two numbers that she gave us.

So they invented a thing called secret jumps.

Leah made a secret jump along her number line.

Then she made a jump of five and landed on the number nine.

How long was her secret jump? This is our talk task.

And we're going to do the first one together.

Then I'm going to give you a question to try by yourself.

So, she made a secret jump.

So we don't know how far she jumped.

And then she landed on nine.

I'm going to use my knowledge of inverse equations to help me with this.

So I know that she made a jump of five, from wherever she'd landed on her secret jump and ended up at nine.

So if I start at nine and take away five, I should land in the place that she landed when she had done her secret jump.

I'm going to move my pointer to nine.

I'm going to jump back five.

Can you count with me? One, two, three, four, five.

I've landed on the number, four.

To check, I'm then going to jump from zero to four.

So I think her secret job was four.

And then I'm going to jump on five more and see if I land at nine.

So let's start at zero.

Secret jumping is four I think, ready? One, two, three, four.

Then we're going to jump on five more.

Because from her secret jump, she jumped on five and landed at nine.

One, two, three, four, five.

We have landed at nine.

So if I had the parts four and five, I know that four and five make nine.

And her secret jump was something.

And then she jumped five more to get to nine.

So I took away the five from nine, the part that I knew, and I found out the part that I didn't know.

I started with the whole of nine, and I took away five to find out what the missing part was.

Nine take away five is equal to four.

Four plus five is equal to nine.

It's time for you to have a go.

I'll read the question to you and I'll show you where I would start.

And I'd like you to pause the video and have a go.

Leah made a jump of six and then another secret jump.

She landed on the number 10.

How long was her secret jump? So this time she has made a jump of six.

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

Then she's made her secret jump and she's landed on number 10.

Pause the video here, and see if you can figure out how long her secret jump was.

I think to figure out how long her secret jump was, we should keep going to get to 10 and count as we go and see how far we need to jump.

So we're on six, ready? One, two, three, four.

Because I know my number bounced to 10, and I know that six and four will make 10.

So if she went, if she landed on six, because her first was just a jump of six.

Then she must've had to have jumped four more to reach 10.

Her secret jump was four.

That one was a little bit different because we knew the first jump, but we didn't know the second jump.

So if we know the first jump, we could jump there and then count on to figure out how many more we need.

But if we know just the second jump we might need to take away from our landing place to figure out the answer.

We're going to get to practise this a bit more later, but for now, we're going to leave Leah's number line.

And we're going to find out how Tom plays the game.

Here is Tom's number line.

Tom's number line goes up and down like this.

First, Tom made a jump of three up his number line, then a jump of two.

Where did he land? So Tom, like Leah starts on zero.

And he's going to first make a jump of three up the number line.

One, two, three, then a jump of two.

One, two, he's landed on the number five.

Then Tom made a jump of one up his number line then a jump of five.

Where did he land? So, starting at zero, pause the video here to have a turn.

He made a jump of one up his number line, then a jump of five.

Pause the video to do the jumps.

And when you're ready, press play.

First, Tom made a jump of one then a jump of five.

One, two, three, four, five.

He's landed on the number six.

Five and one make six.

Or the way that we did it was we jump to one first and then five more.

So one and five make six.

So Tom decided too, that it was too easy for Leah, if he told her what both of the parts were that he was adding together.

So he too made a secret jump.

This time, Tom has made a secret jump on his number line.

Then he made a jump of six and landed on eight.

How long was his secret jump? So the last time we worked at one like this was with Leah.

And we knew what her total was.

We knew the whole, where she'd landed at the end.

And we knew what one of the parts was.

So we took away the part to find out what the other part was.

We're going to do the same for Tom.

So we're doing the inverse equation.

Instead of adding them together like we did when we were hopping on the number line, this time we're going to be hopping backwards to find out the missing part.

I'm going to start with my pointer on the number eight and we're going to jump backwards.

Six, because I know that was one of the parts.

Eight is whole, six is a part, I'm missing the other part.

So on eight, and can you count back six with me, ready? One, two, three, four, five, six.

I've landed on the number, two.

So if I'm right, two was his secret jump, which means two is a part and six is a part.

I'm going to check by starting at zero and adding the two numbers together.

So starting on zero and I jump back to sorry, up to one, two, that's his secret jump.

Then I'm going to jump on six more.

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

And I've landed at the number eight, fantastic.

So his secret jump was two.

Two and six make eight.

Eight is made up of six and two.

Then Tom made a jump of four and then another secret jump.

How long was his second secret jump? So this time we started at zero and I know the first jump.

I know the first jump was four.

One, two, three, four.

Then he did his secret jump and landed on seven.

Pause the video here, to see if you can figure out how long Tom's secret jump was.

So if he has landed on four, because that was his first jump, we know that he has to get to seven, seven is the whole.

And we know that four is a part.

We need to find out what the other part is.

So we're going to count on to find out.

Starting at four, we're going to count on one, two, three.

Four is a part, three is a part, the whole is seven.

I've landed on the number seven.

I started by doing the jump I knew to four.

Then I jumped on until I found the number seven and I had to make three more jumps to get to seven.

Four and three make seven.

Four, five, six, seven, correct.

Your independent task is going to be to do a few more of these questions yourself using either Tom's number line or Leah's number line.

So for example, it might ask you to find Leah's secret jump.

First, she jumped to five, then she made a secret jump and she landed on seven.

What was her secret jump? You can either work out by completing the first jump and then counting on to the whole to find out what the other part is.

Or if you have a part that you know, and do you know what the end is, you can take away like we did for a couple of our examples to find out where they would have started from.

When you're finished, if you try and add the two parts together, to make sure that they make the whole, you'll know that you were correct.

When you finished answering a few of their questions, why not try and come up with a secret question of your own.

You could start with the whole, have two parts and then make one of them are secrets and show it to a talk partner, parent or carer and see if they can figure out what your secret jump was.

It's a really fun game to play.

When you're finished, press play.

So we're going to go through the independent task together now.

And we're going to look at the answers.

So if you have yours in front of you, you will be able to check to find out if you were correct or not.

So, using Leah's number line, try to solve her secret jumps.

Number one, Leah made a secret jump and then a jump of five.

She landed on the number seven.

How long was her secret jump? So for this one I would go to the end.

I know that she landed on seven at the end, and I know that her second jump was five.

So I'm going to count back five.

One, two, three, four, five.

So I think her secret job was two.

Two and five make seven.

Five, six, seven.

If I add the two parts together they do make seven.

But I'm going to check by starting at zero and seeing if I'm correct.

So I think her secret job is two.

One, two, and then the jump I know about is five.

One, two, three, four, five.

And I've landed on the number seven.

So two and five do make seven.

Her secret jump was, two.

The next question says Leah made a jump of two, and then she made a secret jump.

She landed on the number nine.

How long was her secret jump? So for this one, instead, I'm going to start on the number zero.

And I'm going to make the jump that I know about.

I know the first jump was two.

So I'm going to count on.

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

So two and seven, make nine.

Seven, eight, nine, I think that's correct.

But I'm going to check by coming back to the beginning, going to zero, and I'm going to count on two and then seven.

To make sure that I land on nine again.

So she made a jump of two.

One, two, and then her secret jump of seven.

One, two, three, four, five, six, seven, and landed on the number nine.

I could also check by taking away seven.

Because if I land back on the number two, which is the jump that I know she did first, I should be able to find the second part.

I know that two is a part.

So I can check by, taking away as well.

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

So it works both ways too.

Now let's try and solve Tom's, using Tom's number line.

So they are the same numbers and they're very much the same.

They have the same distance between them and they're both number lines, but Leah's is along and Tom's is up.

So Tom's is a bit like climbing a ladder.

Tom made a jump of four and then a secret jump.

He landed on the eight.

How long was his secret jump? Starts at the number zero and jump on four.

One, two, three, four.

That's his first jump.

And then he made a secret jump and landed on the number eight.

When I was working this one out, I thought that I could use my knowledge of double numbers to help me solve this, without even needing to really look at the number line.

Because if I've jumped to four already and he's going to land on the number eight, I know that four and four make eight, double four is eight.

So I think he's added four again, for his secret jump, ready? One, two, three, four.

I was correct.

So four is a part, four is a part, the whole is eight.

Tom's secret jump was four.

He made two jumps of four.

The next question, the last one.

Is Tom made a secret jump and then a jump of two.

He landed on the number five.

How long was his secret jump? So I'm going to start this time, where I know part of the equation.

I know that five was the whole, I know that two is a part.

So I'm going to take those two away.

One, two, I've landed on the number three.

That means three must be the secret jump.

Three is the first part.

And then two is the second part.

Let's check, let's start again.

Zero, one, two, three.

That's three is a part.

And one, two.

Two is a part.

Three is a part, two as a part, five is the whole.

I've ended up at the same place.

So his second secret jump was three.

Did you come up with any secret jumps of your own? If you did, I'd love to hear about them.