Lesson video

Hi, and welcome back to our third lesson, estimated mass.

In today's lesson, we are going to be using our prior knowledge to create good estimates for different masses and then finding the difference.

Okay, let's begin.

So let's go over our lesson agenda first.

First, we're going to be using our prior knowledge for estimating, then we're going to be finding the difference and then we're going to be going into our independent task where we're going to feel confident and then when we go over the answers.

So what you will need today, you're going to need a pencil, a rubber, exercise book, and some utensils that I'll show you later.

Okay, and before we start, because we're going to be using different resources from around the house, like in the kitchen, I want us to be really, really careful when we go and collect these items. So please make sure you ask an adult before you go and reach any high cupboards, safety first, because I really want to make sure that whatever we use, we are being very careful.

So let's start with this question.

Would you weigh these items using grammes or kilogrammes? So you have a fridge freezer, a watch, a toothbrush, a tennis ball, a very large dog, a child, a teacher, a football, a kitten.

I'm going to give you a minute to decide, off you go.

Okay, so we're back.

So let's have a look.

Now before we get started, this is what we're going to be thinking about today, an appropriate unit of measure.

Now when we are measuring with kilogrammes, because we know that one kilogramme is equal to 1000 grammes, then when we're measuring with kilogrammes, those are normally bigger items, okay? But when we are measuring smaller items, then we would be using grammes.

That would be the appropriate unit to use.

So in that case, I'd say that the fridge freezer you would measure in kilogrammes.

I would say that the child you would measure in kilogrammes, a teacher in kilogrammes, a very large dog in kilogrammes, a kitten in kilogrammes, as oppose if the kitten's very small, but I would say that would probably be a kilogrammes.

A toothbrush, would you measure that in kilogrammes? No, because is a lot smaller.

So you'd measure that in grammes, a watch should be in grammes, a tennis ball would be in grammes and a football would be in grammes.

And that's all we're thinking about today, an appropriate unit of measurement kilogrammes or grammes.

And how many grammes are there in one kilogramme, 1000 grammes.

Well done, right, let's move on to the next slide.

Okay, so for our next task, we're going to be proving why it is more practical to weigh heavier items in kilogrammes and lighter items in grammes.

So you're going to need a few items, here we go.

You're going to need a weighing scale, okay? You're going to need a banana, you're going to need an item at home that weighs about one gramme.

Now we said that that's the paperclip.

I've got a, I've just got a few staples, and you're going to need a bag of flour or sugar that would weigh about one kilogramme, okay? So I've got a bag of flour that weighs about one kilogramme.

Now this is going to help us with our next task.

So the first thing I'd like you to do is, is I'd like you to pick up your one gramme items, so that may be a paperclip or in my case my staples and you're going to hold it in one hand like, hold on, let me get, one hand like this, okay? And you're going to just think about the weights of this paperclip.

This is one gramme.

You're, then going to grab your banana first and you're going to hold it in other hand, okay? And I would like you to think about, do you think the banana weighs more than one kilogramme? And you can have a weigh, and if you do this with your items and again if you don't have the items that's okay, I'll explain how it feels like.

The banana feels a lot heavier.

So if this was a natural weighing scale, because it's heavier, then the banana would actually fall down like this, okay? So now what I'm going to ask you to do is, is that we can say that the banana weighs more than the paperclip or one gramme.

Now what I'm going to do is, is I'm going to swap my gramme item and I'm going to for my one kilogramme item.

I'm going to hold in my hand like this, just as we did before, and then I'm going to grab my banana and then we'll go into weighing.

Now I'm going to see which one feels heavier.

I can just estimate in just by how it feels.

Now in this case, the one kilogramme bag actually feels heavier than the banana.

So then it would go like this, right? No, remember that if it's heavier then it goes lower on the weighing scale.

So this one kilogramme is heavier than this banana.

So I can say that the banana is more than one gramme but it is less than one kilogramme.

Okay nice, let's move on.

All right, okay.

So we need to figure out something closer.

So I know that one kilogramme was a lot heavy in the banana, so now I'm going to use this, I'm going to use something at home that weighs 500 grammes, okay? Now so what I'm going to do is, is I'm going to hold it in my hand like this and I'm going to look at the difference, okay? Now this seems a lot closer to the weight of a banana, but this is still heavier, okay? I'd say a lot, still a lot heavier, so it goes down like this.

In that case, I would like you to think about what would be the greatest estimate for a banana, okay? And what we're going to do is we're going to do it to the nearest one 100 grammes.

So thinking about, how many bananas would it take for it to be equal, for our balance to go like this? Okay, so what I'd like you to do is, is in your book I'd like you to write down the estimate in grammes of the banana right now, and then I'm going to show you the actual mass and then you can right next to it, off you go.

So as we can see that our estimate may not have been correct, but what we need to understand is that estimating is a skill and we need to practise, and that most of us won't be very good at it when we begin with like most things.

A good estimate at this stage is one that is correctly lighter or heavier, then we're going to go with 500 gramme mass, okay? And that's all we're going to be using today.

So for our main bulk of our tasks, we're going to be comparing it to 500 grammes because we realised that one kilogramme is far too heavy, okay? But we are going to be better at this guys, I know I believe in us.

Here we go, let's go into the next slide.

All right, so we're now going to be using prior knowledge for estimating, but before we start, I would like to go over our greater than or less than symbols, okay? So remember that greater than is like this and less than is like this.

Okay, so before we start, we're going to play a little game.

On your piece of paper, I'd like you to do this draw the sign for greater than and less than, and when I say it, you go into just quickly just show me.

I know I can't see it but this is just how I would do it in my class.

So just pretend that I can see.

Okay ready, here we go.

And this you're drawing in your books, good.

Greater than, good.

Less than, greater than, greater than, greater than, less than, greater than, less than, less than, less than, less than less than less, good.

Well done guys.

It's important that we're confident with the signs because I'll be using them for the rest of this lesson.

Okay so, when we are using this vocabulary, it is really important.

We're mathematicians and we want to make sure we're using the correct vocabulary when we are estimating.

And we're going to be focusing on the 500 grammes and my 500 grammes is going to be this item right here.

500 grammes in one hand.

So I'm going to start us off.

So I'm comparing it to a kind of pop.

So I know this mass weighs 500 grammes, always start by saying how much the mass weighs you're comparing it to.

The kind of pop, it feels a little bit lighter.

So I estimate that the mass of this tin or can, is 400 grammes, okay? So because it's lighter, I estimate that it's 400 grammes.

The next person would say, "The mass of the kind of pop is 450 grammes." 'Cause they've actually measured it.

You are right.

It is lighter than 500 grammes and that's what we're going to be doing.

Okay, so now we're going to be comparing it to a size of a book, okay? So it's going to start like this.

I know that the mass weighs 500 grammes, always start by acknowledging the main mass you're comparing with.

The book feels about twice as heavy as the mass, so I estimate that the mass of a book is well, twice means times two, 500 times two.

Well, if I know five times two is equal to 10, 50 times two is equal to a 100, so 500 times two is equal to 1000 grammes.

1000 grammes, 1000 grammes is equal to one kilogramme.

We know that this is awesome.

So sorry, let's go back.

So the book feels about twice as heavy as the mass, so I estimate that the mass of the book is 1000 grammes, one kilogramme.

The mass of the book, once I've measured it, is 700 grammes.

So you were right, it is heavier than the 500 gramme mass.

Now as you can see, she wasn't exactly correct but she was able to estimate that it was heavier than the 500 gramme mass, and that's what we're aiming to do today.

So we're going to be using a bag of sugar, flour, coffee from home, to help you complete the following task.

Right, so I will be using this mass right here of 500 grammes.

Now I will be comparing it to a glass that I, just a normal glass in the house, okay? You can choose any item that you would like, right now it doesn't matter that we say that same mass but something roughly around this size in your house you can use.

So I'm going to give you some time right now to pause and go find that.

Okay, so we're ready.

Here we go.

Now I'm going to start off first.

So I know that this mass is 500 grammes, the glass feels, now it says a bit, I can say a little, a lot, it's a bit, a bit much heavier, lighter, twice as heavy, half as heavy, three times as heavy, five times.

I'm going to say it's about half the mass.

So I'm going to say that the glass feels half of the mass.

Okay, lighter, okay? So I estimate that this mass of the glass is about, well, half of 500 is 250, so I'm going to say 250 grammes.

I'm now going to measure it, here we go.

Okay, so I just saw the mass of the glass was 327 grammes.

So I was correct and it was lighter.

I'd like you to try this now at home, you can use the help in estimating language underneath and try different items and see how you get on, okay? Off you go.

Okay, so now we're going to be finding a difference and we're going to be using bar models to help us do that, okay? So what I'm going to ask you to do now is this.

In your books, take one clean page and do three columns.

And you're going to put one estimate, one actual mass, and one difference, okay? Now this is how it's going to work.

Now we're going to start off with the following question, which is the one we did before.

Now, our estimates for the glass was 250 grammes, so I'm going to put it into that column, okay? We then measured it and then we would write it out that it was actually 327 grammes, okay? Now, to work out the difference, I'm going to use this bar model.

I'm going to put the greatest quantity in here, which is 327 grammes.

Now remember that it is the greatest quantity, it isn't always going to be the actual mass.

You then go into go and put in the smaller quantity, which is 250 underneath here, and then you're going to work it out by saying 327 take away 250, to work out the difference.

Now let me think.

How am I going to do that? Well, from 250 to 300 is 50, from 300 to 320 is 20.

So 50 plus 20 is 70 plus the seven is 77, okay? And as you can see on my bar model, I've worked that this is also 77, right? Can you guys help me out for the next one? We're going to think back to our banana, all right? So my estimate for the banana was actually 130 grammes, and then we then worked out the actual mass, let's see if can remember it, was 198 grammes.

So therefore the greater quantity is 198, well done.

Smaller quantity then is 130, and in order for us to work out this difference, we need to do what? 130 to take away 198? No, absolutely not.

Remember it is the bigger bar model take away the smaller quantity, which is this one right here, and we should have this calculation, 198 take away 130 and now I'm going to use my mental arithmetic.

Well, I know that from 130 to 190 is 140, 150, 160, 170, 180, 190 is 60, and then plus then from eight, that 68.

And as you can see, I've also added that to my bar model.

Well done guys, really good work from you.

Well done guys, now it's your turn, okay? We're going to be using these two estimates.

So my estimate was 300 grammes and the actual mass was 275 grammes.

What is the correct answer? Pause the video and work it out now.

Okay, so let's see how we got on and your answer should have been, this one right there.

Let's figure out the working out then.

So if the estimate was 300 grammes, look, this is what I said to you earlier.

The actual mass won't always be the greater quantity.

So in that case, the great quantity here is 300 grammes which goes at the top, which is our bigger model, actual mass then is our smaller quantity and now we need to put it into our calculation.

300 grammes takeaway 275 grammes, which is equal to 25 grammes.

Okay, it's time for your independent task.

What I've tried to do is I've tried to choose four items that hopefully we all have at home.

If you do not, maybe you can then choose your own items that you think roughly might weigh the same.

And if you have a weighing scale, then you can also work out that your mass, and if you don't, don't worry, I will show you the actual mass.

So I have gone for a mug, okay? My favourite mug, I have gone for a book 'cause I love books and reading is important guys.

So let's hopefully we've all got, easily be able to find a book, which is about 348 pages long, okay? So this is my book.

I've gone for a shoe, a white shoe right here.

Okay, a size nine shoe if you really want to be exact with me.

Okay, size nine shoe, and I have gone for a standard cereal bowl right here, okay? Now, remember when we are estimating, we are going to be using 500 grammes as helping us estimate, okay? So have one hand and hold it another, and this is the action you're going to be doing.

So if you're going to start off with a mug, so if you're going to estimate, you're going to hold the 500 grammes in one hand, the mug in other, and you're going to measure and see which one do you think is heavier or lighter than 500 grammes.

Is the first one you're going to say, and then you go in to estimate the mass.

Good luck guys, I wish you all the best, it's going to be amazing, go to your worksheets, fill in the estimates.

If you have a scale, fill in the actual mass and then come back to me.

Can't wait to see it.

Okay, so let's measure the mug and the mug is 343 grammes.

The book weighs 247 grammes.

The shoe weighs 338 grammes, and the bowl weighs 390 grammes.

Okay, so here are answers, okay? So as you saw from the video, we came up with the actual masses there, and these are my estimates.

Now, roughly you should have worked out that yet, that the mug, the book, the shoe and the bowl were lighter than the 500 gramme mass, okay? The one that was slightly surprising for me, might have surprised you, was maybe the shoe.

'Cause I think we normally think, Oh, well, a shoe is definitely going to be heavier than the 500 grammes 'cause it looks bigger, but I think it depends on the material of the shoe.

My shoe is actually quite light.

I reckon if I used like a leather boot with a heel, might be heavier.

Okay, now what I would like you to do is I know that some of you may already have your own estimates and actual masses, but I actually would like you to use mine just so then we all have the correct answer for the next part, okay? So you're now going to go back to the worksheet, to the worksheet two or task two, and you're going to work out the differences.

Don't forget to use your bar models guys.

I'd love to see some pictures of some bar models using that to help you, okay? Good luck.

Right, let's find the answer to the question.

So then if we start off with the mug right here, then we know that estimate is 300, the actual mass is 343, therefore a great quantity is 343 grammes, our smaller quantity is 300 grammes.

We're going to put it into this calculation, okay? 343 take out 300, nice and simple for us is 43, okay? And don't forget to put it into your bar model.

Okay, here we go, next one.

Our book was 220 estimate, actual mass is 247.

So the great quantity is 247, the smaller quantity is 220, and the difference what? Were you going to put into the calculation first? And that's 247 take away 220.

So from 220 to 240 is, 230, 240, 20 plus the seven 27, okay? Honestly, you guys can't wait to see your bar models, it's going to be really good.

All right, next one.

We have our shoe right here.

Again, surprised me.

I went for a slightly higher, I think I went for misconception that is, because it's a bigger item and it looks big, I thought it would be heavier and that isn't always the case, okay? So 450 grammes was what I estimated, ended up being 338.

So my bigger value, my quantity goes to the top, smaller quantity at the bottom.

I put into my calculation and okay, let's have a look then.

So from 338, what I'm going to do is, is I know that if I add two, it goes to 340, to 340 to 460, so that's 62 to plus 50 gives me 112, okay? So that's my answer there.

And finally our lovely bowl, okay? And the estimate was 400 and I did quite well here.

I have the actual mass 390, I hope you guys did well too.

And then I put into my calculation and this was nice and simple, the difference is 10, okay? Okay, so that brings us to the end of today's lesson.

A really big well done to all the fantastic learning you've achieved today, and being able to be really safe with all your equipment.

Finally, could you please, when you finish this, take the quiz so you can then test yourselves and see what you've learned today.

Well, well that's I have to say is thank you, take care and enjoy the rest of your learning for today.