Lesson video

Hello, my name's Mrs. Hopper and I'm really looking forward to working with you in this maths lesson.

So, if you're ready to work hard, let's make a start and see what this learning is all about.

So welcome to this lesson about explaining the difference between consecutive odd numbers and it's from our unit, "Addition and Subtraction Facts within 10." So by the end of this lesson, you'll be able to explain the difference between consecutive odd numbers and use them to solve problems. Let's have a look at what's in our lesson.

We've got some key words in our lesson, so let's practise them.

I'll say them first and then you say them back.

So my turn, difference, your turn.

My turn, odd, your turn.

My turn, consecutive, your turn.

Well done, you may well have come across those words before, but they're going to be useful, so look out for them in today's lesson.

There are two parts to our lesson today.

In the first part, we're going to find the difference between consecutive odd numbers, and in the second part, we're going to use that knowledge of consecutive odd numbers to solve problems. So let's get started.

And we've got Sam and Jacob helping us in our lesson today.

Sam and Jacob were getting ready to go on a picnic.

Lucky them.

First, they had to get the sandwiches ready.

So, first, Sam and Jacob made five sandwiches.

Then, Jacob ate three of the sandwiches while he was making them.

He must have been hungry.

So there are the three sandwiches that Jacob ate.

Now, how many sandwiches were left for the picnic? Let's represent the problem as a bar model.

First, there were five sandwiches, so we're representing the sandwiches as counters in our bar model.

Then three were eaten.

Jacob says, "I think you at them, didn't you Jacob?" "So we're solving," he says, "Five, subtract three." So, five subtract three.

So five is our whole, three is a part.

What is our other part? Sam says, "Three is two less than five." "So there must be two sandwiches left for you, Jacob." That means Jacob's eaten all the sandwiches.

Does Sam not get any sandwiches? Five subtract three is equal to two.

Now they need to pack the fruit for their lunch and for their snack, as well.

So, first, they collect seven pieces of fruit.

Oh, that looks good, doesn't it? Then, they put away five to have with their lunch.

So there are five pieces of fruit for their lunch.

Now, how many pieces of fruit will they have left for their snack? Let's represent the problem as a bar model.

First, there were seven pieces of fruit.

So there are seven counters to represent the fruit.

Then, five will put away for lunch.

So Jacob says, "We're solving seven, subtract five." So seven subtract five.

Seven is our whole, and five is the part that's been put away for lunch.

Sam says, "Five is two less than seven." "So there must be two pieces of fruit left for our snack." And there they are, the two pieces of fruit for the snack.

Jacob looks at the equations from both problems, together.

Do you notice anything? We've got the bar models there to help us, as well.

Five subtract three equals something, and seven subtract five equals something.

Jacob says, "The wholes and the known parts" "are all odd numbers." "Five and three." So five as the whole three is the part that we took away, the sandwiches that Jacob at.

They're odd numbers.

And seven pieces of fruit and the five pieces of fruit that they put away for their lunch.

They are both odd numbers.

He says, "They're all odd numbers." "Three, five, and seven." "And they're odd numbers that are next" "to each other when we count in odd numbers" "along the number line, and we can see them there." "Three, five, and seven." "This means that the equations" "will have a difference of two." Because we can see that those odd numbers are two apart on the number line.

So, five takeaway three is equal to two, seven takeaway five is equal to two.

We can see that those missing parts in both equations are equal to two.

Let's identify the odd numbers on our number line.

The odd numbers are the ones that are not made from two.

So they've got the extra one sticking out each time.

So let's have a look.

We've got one, and we've got another one there, we've got three.

And the next one is five.

Then we've got seven, and then we've got nine.

Let's count in odd numbers, shall we? Let's count up from one to nine in odd numbers and then we'll go backwards, as well.

So let's count up from one.

Are you ready? Let's count.

One, three, five, seven, nine.

Well done.

Should we count backwards from nine to one in odd numbers? Let's count from nine, are you ready? Nine, seven, five, three, one.

Well done, good counting.

It's always good to practise counting, especially backwards 'cause that can be a bit trickier.

Let's have a look at these numbers as we count, one, three, five, seven, nine.

Do you notice how big the jump is each time? We can say that consecutive odd numbers.

So the odd numbers that are next to each other when we count in odd numbers, consecutive odd numbers have a difference of two.

We've got to make two jumps on the number line to get from one to three and then from three to five and then from five to seven and then from seven to nine.

And the same going backwards.

So three and five are consecutive odd numbers.

They're next to each other, when we count in odd numbers.

"Sam says three and five have a difference of two." "We can say that five is two more than three," "and three is two less than five." Time for you to have a check of your understanding.

Use the number line to find more consecutive odd numbers and use the stem sentences to help you.

So hmm and hmm are consecutive odd numbers.

Hmm is two less than hmm.

And hmm is two more than hmm.

See how many different pairs you can find? Pause the video and then we'll have a look at them together.

How did you get on? Did you spot one and three are consecutive odd numbers? So we can say one and three are consecutive odd numbers.

One is two less than three, and three is two more than one.

Jacob says, "You could have had a few different pairs." I wonder what else you found? "You could have found three and five," "five and seven, seven and nine." I wonder if you found all of them? Time for you to do some practise.

You're going to sort these expressions to show which represent a difference of two.

So we've got some bits of subtractions there and you're going to find the ones that have a difference of two.

Maybe you can look for those consecutive odd numbers.

You can sort them, ones that have a difference of two, and ones that do not have a difference of two.

Pause the video, have a go, and then we'll talk through it together.

How did you get on? Did you manage to sort them? Let's have a look.

So let's start with the ones that do have a difference of two.

Five subtract three.

Five and three are consecutive odd numbers, so they will have a difference of two.

So we can record that one there.

Five takeaway three equals two.

Eight subtract seven.

They're not odd numbers, are they? Eight is an even number.

So we don't have consecutive odd numbers there.

So eight minus seven will not have a difference of two, but they are consecutive numbers when we count in ones, so there'll be a difference of one.

What about three subtract one? Yes, you're right.

That one does have a difference of two.

They're both odd numbers.

What about five and one? Five subtract one? Well, they're both odd numbers, but they're not consecutive, are they? If we count up in our odd numbers, one, three, five, no, we have a three between one and five.

So they do not have a difference of two, even though they are both odd numbers.

What about seven takeaway six? Oh, six is an even number, isn't it? So those are consecutive numbers when we count in ones.

So they will have a difference of one.

What about nine and five? Nine subtract five? Well, nine and five are both odd numbers, but let's count.

Are they consecutive? One, three, five, seven, nine.

No, they're not consecutive are they? So they're both odd numbers, but they're not consecutive.

They have a difference of four.

What about nine subtract seven? One, three, five, seven, nine, or nine, seven, five.

Yes, they are, aren't they? They're consecutive odd numbers.

So they will have a difference of two.

And seven subtract five.

One, three, five, seven.

Yes, they're consecutive odd numbers as well, aren't they? So they will have a difference of two.

Well done if you got all those sorted correctly.

So, we're into the second part of our lesson.

This time we're going to use our knowledge of consecutive odd numbers.

Sam took nine slices of cake.

Seven were eaten at the picnic.

How many slices does Sam have left? So Sam started with nine and seven were eaten at the picnic.

Hmm? Let's have a think.

Sam says, "We can represent this as a bar model." "Nine is the whole and seven is a part." So nine was the whole, the number of cakes we started with, and seven of them were eaten.

So seven is a part.

They've been eaten already.

How many slices does Sam have left? Jacob says, "I will count back seven from nine" "to find the difference." "Nine subtract seven." Sam says, "Wait, there's a quicker way." "We don't have to count back in ones." "Look at the whole and the known part." So the whole is nine, and the known part is seven.

Do you spot something? "One, three, five, seven, nine," Jacob's counting.

"Oh," he says, "They are consecutive odd numbers." "Consecutive odd numbers," Sam says, "have a difference of two." "So that means the missing part is two." So there must have been two slices of cake left when seven were eaten.

Here's some more to do with their picnic.

Sam and Jacob took three bottles of juice to drink.

Now they have two left.

How many did they drink? Hmm.

Might be different ways to think about this, but let's think about it using our consecutive odd numbers and see if we can work our way through the problem.

thinking about those.

Jacob says, "We had three bottles at the start." "So three is the whole, and we had two left." "So two is a part." So they're using a part, part whole model this time.

Three was the whole and two is a part.

Sam says, "I know consecutive odd numbers" "have a difference of two." "Does this help us?" "Yes!" says Jacob.

"Let's find the odd number that comes before three." So there's three.

Sam says, "I can see one is the odd number before three." "So this will be the missing part." One and three are consecutive odd numbers.

They have a difference of two.

Jacob says, "That means we drank one bottle." So they must have shared it, mustn't they? And Sam says, "I know we are correct," "because when I added two and one," "the whole was three and three is one more than two." So we can figure out it that way as well, can't we? Time for you to check your understanding.

The children took seven pieces of fruit for the picnic.

They've eaten two pieces so far.

How many pieces of fruit do they have left to eat? So we've got a part, part, whole model, seven was the whole number of pieces of fruit we took, and they've eaten two pieces.

So that was our part.

What is our other part? Pause the video, have a think, and then we'll talk it through together.

How did you get on? So seven is the whole, that was all the fruit they took to the picnic, and two is the known part.

We know this part, that's the part they ate.

We know that consecutive odd numbers have a difference of two and we can use this to help us.

So we know that our whole is an odd number, seven.

And we know that there's that difference of two there, the two pieces that have been eaten.

So the odd number before seven is five.

Seven take away two is equal to five.

So, Jacob and Sam have five pieces of fruit left to enjoy.

Seven and five are consecutive odd numbers.

So the difference, the other part, must be two.

Sam has hidden the numbers in some equations.

What do we notice about these equations? Anything you notice as you're looking at them? Hmm, I wonder? Ah! Well, we know that in each equation there's a difference of two.

Nine subtracts something equals two.

Seven subtracts something equals two.

Five subtract something equals two.

So the difference in each is two.

And we can also see that the whole, the number we're starting with, you might notice the minuend is an odd number in each case.

Nine, seven and five are all odd numbers.

Jacob spotted something.

Jacob says, "The whole and the other part" "must be consecutive odd numbers" "because we know that consecutive odd numbers" "have a difference of two." And we know that the difference for all of these is two.

So we're looking for consecutive odd numbers.

"In each equation the hidden part" "must be two less than the whole." All Sam says, "Well, two less than nine is seven." So this one must be seven.

Nine subtract seven is equal to two.

"Two, less than seven is five." So seven, subtract five must be equal to two.

"And two less than five is three." So five subtract three must be equal to two.

So they've used their knowledge of consecutive odd numbers to find out what the missing numbers were in those equations.

Time for you to do some practise now.

There are some missing numbers to complete in these part, part whole models and equations.

I wonder if you can use your knowledge of consecutive odd numbers to help you.

And then for this part we'd like you to fill in the part, part whole models in as many different ways as you can using consecutive odd numbers.

So pause the video here, have a go at your tasks, and then we'll look through the answers together.

How did you get on? Did you use your knowledge of consecutive odd numbers to fill in the missing parts of these part, part whole models and equations? So let's look at A, the whole was nine and one part was seven.

Are they consecutive odd numbers? They are, aren't they? So the missing part must be two.

Nine subtract seven is equal to two.

For B, we've got the whole is five and one part is three.

Are five and three consecutive odd numbers? They are, aren't they? So the missing part must be two.

Five subtract three is equal to two.

For C, we've got three as our whole, and two as our part.

So we know the difference is two.

So we know that our missing part must be at the consecutive odd number to three.

So it must be one.

Three subtract one is equal to two.

Our missing part is one.

And for D, we've got our whole is seven, and the part we know is two.

So that's our difference, isn't it? So we know that the missing part must be a consecutive odd number to seven.

So seven subtract five is equal to two.

Seven and five are consecutive odd numbers.

So the difference will be two.

So hopefully you use your knowledge of consecutive odd numbers that always have a difference of two to fill in these part, part whole models.

I wonder how many different ways you've found to do it? You might have had three as a whole and one as a part.

Three and one are consecutive odd numbers.

So the difference must be two.

You might have had five as the whole and three as a part.

Five and three are consecutive odd numbers.

So the difference must be two, the other part.

You might have had seven as your whole and five as your other part.

Seven and five are consecutive odd numbers.

So the other part, the difference, must be two.

And finally, you might have found nine as your whole and seven as your part.

Nine and seven are consecutive odd numbers.

So the difference, the other part, must be two.

Well done if you've got all of those different possible answers.

And we've come to the end of our lesson explaining the difference between consecutive odd numbers.

What have we been learning about? We've learned that consecutive odd numbers have a difference of two, they're two apart when we jump on the number line and we count in odd numbers.

And we can use this knowledge to solve missing number problems when two is the known part, we know that the whole and the other part must be consecutive odd numbers.

Thank you for your hard work and all your thinking today and I hope I get to work with you again soon.

Bye-Bye.