Lesson video

Hello, welcome, welcome to your math lesson for today.

My name is Dr.

Shorrock, and I am very much looking forward to helping you deepen your understanding of the maths that we will be looking at today.

Today's lesson is from our unit measures, mass and capacity.

The lesson is called Measure the Massive Objects using grammes.

We are going to look at using scales, that have got different intervals to measure the massive objects and to compare their masses.

Don't worry if the learning gets a little bit tricky.

I'm here to guide you and help you.

And I know if we work really hard, we can be successful in this learning.

So, shall we find out, how do we measure the massive objects using grammes? These are the key words that we will be using in our lesson today.

We've got mass and gramme.

I'm sure you may have heard those words before, but shall we practise saying them anyway? Are you ready? My turn.

Mass.

Your turn.

Brilliant.

My turn.

Gramme.

Your turn.

Fantastic.

So when we talk about mass, we mean how much matter is inside the object and we commonly measure it using how much something weighs.

And it's measured in grammes.

That is the unit that we will be talking about in our lesson today.

And a gramme is a metric measure of mass and I dunno if you can find a paperclip or ask an adult to find a paperclip for you.

But if you hold a paperclip, that paperclip has got a mass of about one gramme.

And in maths we like to abbreviate, and we abbreviate the word gramme two a lowercase g.

So if you see that lowercase g throughout our learning today, you know we mean gramme.

So today we're going to look at measuring the massive objects using grammes.

That's where we're going to start our learning.

After that we'll look at how we compare masses of objects using grammes.

These are the characters who are going to help us today.

We've got Aisha, Sophia, and Andeep.

So, sometimes we need to know the actual mass of an object.

One example I can think of is when we need to send an item in the post, maybe you or someone you know has had to send something in the post, and you need to know how heavy it is, what it's mass is, and that's how they work out, how much postage you have to pay.

So Sophia wants to send this toy panda in the post as a gift to her cousin.

She's going to need to know the mass of the toy panda.

And she can use scales to measure the mass.

So what is the mass of this toy panda? Oh yes.

Sophia is telling us the mass of the toy panda is between 300 and 400 grammes.

Can you see that? That arrow is pointing to between 300 and 400.

But yes, that's right Sophia, when we send something in the post, we need to know it's accurate mass.

What actually is the mass of the panda? We can't just say, oh, it's between 300 and 400.

We need to know what it is accurately.

When we accurately measure the mass of an object, we need to determine the value of those unmarked intervals.

We can see that arrow is pointing to an unmarked interval.

There's no number by, it's between 300 and 400.

The marked intervals we can see are increasing by 100 each time we've got 0, 100, 200, 300, 400.

So those intervals are going up by 100 each time.

And can you also see there are two equal parts in between those marked intervals? We know that 100 is composed of two 50s, so each of those parts must be worth 50 grammes.

And the arrow is pointing to the end of the first part in between 300 grammes and 400 grammes.

So that means we can say that the arrow is pointing halfway between 300 grammes and 400 grammes and we can count on then we know the scale is going up in 50.

So we can count in 50s, we're gonna start at 300 because that's the first full number that we know.

So we've got 300, 350, 400.

But where's the arrow pointing? That's right, to the 350 unmarked interval.

The mass of the toy panda is 350 grammes.

So let's check your understanding.

Can you tell me what is the mass of the orange? You've got three options, 110 grammes, 150 grammes, or, the arrow is not pointing to a marking tool so you cannot tell.

Pause the video and when you think you know press play.

How did you get on? Did you notice that the mass of the orange is 150 grammes? But why? Well maybe you notice that there are two parts between each interval, and each part is worth 50 grammes, and the arrow is pointing to the end of that first part.

And we can count on in 50s from that known interval number 100 and then 150, 200.

But the arrow is pointing to the 150 grammes.

The mass of that orange is 150 grammes.

Well done.

We've got Andeep and Aisha now, and they've both found a rock when they were playing outside.

"I wonder how heavy our rocks are," Aisha is wondering.

Andeep is correcting her here.

Really she should be saying, we wonder what the mass of each rock is.

That's the correct terminology, we should be using mass.

So Andeep and Aisha decided to use a new scale.

Can you see what the mass of an's green rock is? That's right.

It's quite easy to see the mass of Andeep's rock because the arrow is pointing directly to that 200.

So the mass of the rock is 200 grammes.

Ah, what do you notice here? Aisha's got it a little bit trickier, hasn't she? Can we work out what the mass of herb brown rock is? Well we can say it's somewhere between 200 grammes and 300 grammes.

To work out the mass of Aisha's rock, we need to look at the value of those unmarked intervals and we need to look at that part of the scale.

And have you notice with scales, they're just number lines but they're curved.

So I'm going to unroll this number line here, and you can see the part that I'm looking at starts at zero and ends at 100.

And we can use this to help us calculate those unmarked intervals so that we can work out the mass of Aisha's rock.

Can you see there are five equal parts between the marked intervals.

We know that 100 is composed of five equal parts of 20.

So 100 grammes must be composed of five equal parts of 20 grammes.

You can see I've marked that on my straight number line now.

20, 40, 60, 80.

The arrow is at the end of the second part after 200.

So we can count on in 20s from 200 to work out the mass.

We've got 200, 220, 240.

The mass of the pebble is 240 grammes.

Let's look at a slightly different example.

Let's work out the mass of this toy car.

Maybe you've noticed something about the scales already.

Andeep is saying the mass of the toy car is 130 grammes.

I can see why he thinks that, can you? Aisha is disagreeing.

She thinks the mass of the toy car is 160 grammes.

Who is correct do you think? I wonder if you think, oh yeah, I agree with Andeep, or I agree with Aisha.

Shall we find out? So first we need to work out how many equal parts there are in between the marked intervals.

And that's true every time you see a scale you need to work out the number of equal parts in between those marked intervals.

It's a really useful thing to do.

There are five equal parts in between the marked intervals.

We know 100 is composed of five equal parts of 20.

So 100 grammes is composed of five equal parts of 20 grammes.

And we can unwind the curve scale, and look at it as a number line.

And you can see the arrow is at the end of the third part after 100.

So we can count on from 100 in 20s to work out the mass of the toy car.

We've got 100, 120, 140, 160.

The mass of this toy car is 160 grammes.

Ah, that's right.

Aisha was correct.

So Andeep had just counted on in tens.

But what we need to do is always check how many equal parts there are between the marked intervals and then they used that to help us.

Now let's check your understanding so far.

True or false.

The mass of this cabbage is 375 grammes.

So have a look at that scale very carefully and would you agree with that? Is that true or false? And then choose your justification.

Is it a, there are four unmarked intervals between the marked intervals and each is worth 25.

Is it that there are five parts in between the marked intervals.

Each part is worth 20.

So the mass of the cabbage is 360 grammes.

Press pause on the video and when you think you know press play.

How did you get on? Should we have a look? That's right, it's false.

The mass of the cabbage is not 375 grammes.

It's not 375 grammes because there are five equal parts in between those marked intervals and each part part is worth 20.

So the mass of the cabbage must be 360 grammes.

Let's have a look at a different scale to measure the mass of this banana.

What do you notice about the scale? It's always really important to have a look at the scale.

Ah, Sophia has noticed there are 10 equal parts this time in between the marked intervals.

And as before, we can just show this curve number line as a linear number line to help us find the value of those unmarked intervals.

We know 100 is composed of 10 equal parts of 10.

So 100 grammes must also be composed of 10 equal parts of 10 grammes.

And you can see on my number line, I've labelled those parts now we've got 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100.

The arrow on our scale is at the end of the fifth part after 100.

We can count on from 100, which is the nearest whole number we've got that's marked on the scale, and we can count on from it in tens to find the mass.

So you're going to count with me.

So we'll start at 100, 110, 120, 130, 140, 150.

The mass of this banana is 150 grammes.

Now it's time to check your understanding so far.

Can you work out the mass of this cake? Maybe you would like to find someone and say the sentence completing the blank to them.

But remember, what do you notice about the scale? Press pause on the video and when you are ready, press play.

How did you get on? Did you notice that the mass of the cake is 240 grammes? That's because the value of each part is 10 grammes.

Because 100 is composed of 10 equal parts of 10.

The arrow is pointing to the end of that fourth part after 200.

So we can count on starting at 200, 210, 220, 230, 240.

Let's look at a different scale now what do you notice about this scale? That's right.

Sophia is telling us there are four equal parts this time between those marked intervals.

We can represent this part of the scale as a linear number line to help us, can't we? That's right.

And we know that 100 is composed of four equal parts of 25.

So each of our parts must have a value of 25.

So I've got 25, 50, 75 and 100.

We can use that to work out the mass of this block of cheese.

We can see in this scale there are four parts between each marked interval and each of those parts is worth 25 grammes.

The arrow is pointing to the end of the first part after 200 grammes.

So it's 200 grammes and one more part of 25 grammes.

So it's 200 grammes add 25 grammes, and if we combine those, we get 225 grammes.

The cheese has a mass of 225 grammes.

So let's check your understanding.

Could you tell me what the mass of this orange is? So remember what do you notice about the scale first? Pause the video, and when you think you know the answer, press play.

How did you get on? Did you notice that it must be 175 grammes? But why? Ah yes, that's because there are four equal parts in between those marked intervals of 100.

And each part is worth 25 grammes.

The arrow is pointed to the end of the third part after 100.

So we can start at 100 and we need to add 25, another 25 and another 25, three 25s, which is the same as 75.

So we've got 100 grammes and 75 grammes, and that gives us 175 grammes.

So the mass of that orange is 175 grammes.

Well done if you've got that.

It's your turn to practise now.

So for your first question, I'd like you to have a go at reading these scales.

Can you work out the mass of these objects? For your second question, I have a problem for you.

We've got, Andeep found an apple that had a mass of 125 grammes, and you can see that on the first scale.

Sophia's apple had a mass that was 35 grammes more.

Can you draw the missing arrow on the scale to show the mass of Sophia's apple? Press pause on the video and when you've completed both questions, press play.

How did you get on? Shall we have a look? So the first question, you were asked to work out the mass of these objects.

So you got 75 grammes for the stone, 450 grammes for the gift, 280 grammes for the book, and 290 grammes for the toy car.

For question two you had that problem that Sophia's apple had a mass that was 35 gramme more than Andeeps.

So if we add 35 to 125, we get 160.

So the mass of Sophia's apple must be 160 grammes.

And we know 160 grammes is composed of 100 grammes and 60 grammes.

So we can use that to draw the arrow because 160 grammes we know it must be past the 100 gramme mark, and then 60 is composed of three 20s.

So we know it must be on the mark for the third interval after 100.

Okay, fantastic progress in your learning so far everybody.

Shall we continue? Let's move on to comparing masses measured in grammes.

Sometimes we need to compare masses of objects.

Aisha is wondering which is heavier, orange or the lemon.

What do you think? Oh, Andeep is reminding us we should always use the accurate vocabulary.

So we wonder which fruit has the greatest mass.

Let's compare the mass of these pieces of fruit.

What do you notice? Is there something that you have noticed about those scales already? Sophia is telling us the mast of the lemon is 200 grammes.

That's quite easy to see, isn't it? Because the arrow is pointing straight to the 200.

Sophia has also noticed that the scales are both the same, and there are four equal parts in between the marked intervals.

And that means each part is worth 25 grammes.

And we can use that to help us determine the mass of the orange.

The mass of the orange, that arrow is pointing to that end of that third part.

So the mass of the orange must be 275 grammes.

So the orange has the greater mass, we might say that it is heavier.

So what have we learned about the mass of these pieces of fruit? Well we've learned that 275 grammes is greater than 200 grammes, and we can write that using the inequality sign.

275 grammes is greater than 200 grammes.

The orange has a greater mass than the lemon.

But, did we have to work out both masses to compare these pieces of fruit? Looking at the scales, what do you think? No, we didn't have to work out the masses.

The scales are the same.

And because they are the same, we can use our knowledge of number lines.

The arrow showing the mass of the orange is further along that number line.

So it must have a greater value for its mass.

Let's check your understanding.

True or false.

The toy car has a greater mass than the pair.

Have a look at the scales, think about what do you notice, and say if that's true or false and then justify your answer.

Is it, the toy car is bigger in size so it must have a greater mass? Or, does the pair have a greater mass because the scales are the same and the arrow on the pear scale is closer to 200 grammes? Pause the video and when you are ready, press play.

How did you get on? Did you notice that it's false? The toy car does not have a greater mass than the pear.

The pear has the greater mass.

Because the scales are the same, we can just look at the arrow and think of it as a number line.

And the arrow on the scale with the pear is closer to 200 grammes.

Well done.

So let's compare the mass of these cakes.

Let's think about what we notice first about those scales.

Is there something you notice? What's the same, what's different? That's right.

Sophia has noticed the arrows are pointing in the same direction, but the scales are different.

So their mass will be different.

We need to work out the mass of both cakes before we can then compare that mass.

Let's look at the first cake.

What do you notice? What do you notice about that scale? How many equal parts are there? That's right for this scale there are four equal parts in between the marked intervals of 100.

And we know each part must be worth 25 grammes.

So the arrow is pointing to the end of that first part after 200, so the mass of the cake must be 225 grammes.

If we look at the other cake, this time, this scale is different.

There are five equal parts in between the marked intervals of 100.

We know each part is worth 20 grammes, and that arrow, it's still pointing to the end of the first part after 200, but because the parts are different this time, the mass of the cake is 220 grammes.

So if we put these cakes together, we can see the mass of the orange cake is 225 grammes.

The mass of the green cake is 220 grammes.

So yes, those arrows were pointing in the same direction, but the scales were different.

One had intels of 25 and the other 20.

So if we compare the math of these cakes, we can say 225 grammes is greater than 200 grammes.

We can use that as an inequality.

225 grammes is greater than 220 grammes.

The orange cake has a greater mass than the green cake.

So it's very, very important that we notice the scales and the intervals when we are measuring mass.

Let's check your understanding.

Can you compare the mass of the toy robot and the toy car? I've given you a sentence to use, maybe find someone, see if you can say the sentence to them.

Pause the video and when you're ready, press play.

Okay, how did you get on? Did you work out that the mass of the toy robot was 150 grammes, and that of the toy car was 280 grammes? We needed to work out their masses to be able to compare them.

And once we've worked out their masses, we could see 150 grammes is less than 280 grammes.

Can you represent that as an inequality? 150 grammes is less than 280 grammes.

And then I could complete my sentence.

The toy robot has a mass that is less than that of the toy car.

Now it's your turn to practise.

Question one, I would just like you to complete these equations by filling in the missing inequality symbol.

Are they less than or greater than? For question two, can you tell me which object has the greater mass? Is it the toy rocket or the toy car? And then could you tell me how you know? For question three, I'd like you to determine the masses of these objects.

And then, starting with the lightest, could you put 'em in order of mass explaining how you know? Remember for these questions, take care to look at those scales and their intervals.

What are they going up and how many equal parts are there? So press pause on the video, and when you finished all three questions, press play.

How did you get on? Let's have a look at those inequalities.

So you are asked to complete the equations by filling in the missing symbols.

I'll give you a few moments just to have a look at your work and mark it with these answers.

For question two, you are asked which object has the greater mass? Is it the toy rocket or the toy car? And to explain how you know.

Well the mass of that rocket is 350 grammes.

We can see that because the arrow is pointing to the end of the second part and there are four parts.

So each part is worth 25 grammes.

The mass of the car is 340 grammes.

We can see that because the arrow is pointing to the end of the second part, there are five parts.

So each part must be worth 20 grammes.

So 350 grammes is greater than 340 grammes.

So the rocket has the greatest mass.

Well done if you've got that correct.

Question three, you are asked to determine the mass of these objects and then starting with the lightest, put them in order.

So the mass of the tomato is 175 grammes, the apple 180 grammes, the grapes, 210 grammes, and the orange was 250 grammes.

And you can see I have them put them in order starting with the lightest.

How did I know? Well, some of the masses were greater than 200 grammes, that's the grapes in the orange.

They must be the heavier ones.

The tomato was the lightest, it only had a mass of 175 grammes, and the orange was the heaviest with a mass of 250 grammes.

And that's greater than the other masses.

Well done if you've said something like that.

Fantastic learning today everybody.

You have made such good progress on your ability to measure the massive objects using grammes.

We know that we can use scales to measure the massive objects, but that they can be marked in different ways.

And we know that when we're accurately measuring the massive objects, we need to use those known facts about the composition of 100 to determine the value of the unmarked intervals.

So really well done today, everybody.

I'm really impressed with the progress you have made and I will see you again soon.