Lesson video

Hi everyone my name is ms. Jeremy.

Thank you for joining me for a math lesson.

Today our maths lesson is focused on Roman Numerals between one and 100.

Get yourself sorted with a nice quiet space, free from distractions and once you're ready, press play to begin your lesson.

Let's begin by looking at our lesson agenda.

So we're going to start by talking about what are Roman Numerals actually are and thinking about where you might have seen Roman numerals before.

We're then going to at Roman Numerals between one and 10 before looking at Roman Numerals all the way up to 100.

By the end of the lesson, we will have also completed some Roman Numeral sequences before your independent task and quiz at the end of the lesson.

For today's lesson, you will need a pencil and some paper.

You'll also need a quite nice quiet area free from distractions.

So get yourself sorted with these resources while you pause the video.

And once you're ready, restart the video and join us for the rest of the lesson.

So let's begin the lesson by talking about Roman Numerals, what they actually are.

And I'm going to start with this question here, which asks us, where have you seen Roman Numeral before? I'd like you to spend 10 seconds just having a think about the location, where you might see Roman Numeral before.

10 seconds starting now.

So there are lots of places where Roman Numerals are still used now.

Most often you might find them on clock faces, on watches, if you've ever had a really close look at Big Ben, you'll notice that the number's going all the way around the gauge of the Big Ben clock face are actually Roman Numeral rather than numbers like we see nowadays.

And Roman Numerals are a combination of different letters that taken from the Latin alphabets.

The origins of Roman Numeral, as the names suggests goes all the way back to ancient Rome, and basically these different letters put together represent different numbers that we now use in our normal system nowadays.

The great thing about Roman Numerals and the great thing about learning about Roman Numeral it's a little bit like cracking a code.

If you know what the different letters mean and you know how to place those different letters together with one another, you can represent any number you like.

And the lovely thing about today's lesson is that we're going to be learning how to crack that code so let's get started.

So as you can see on the screen here, we've got, first of all, a list of the numbers that we are familiar with, this is the Arabic Numeral system.

And this has the number system that we use nowadays we're very familiar with it.

Just below it we're going to see whether we can match each of the Arabic Numeral system numbers up with a Roman Numeral.

The first thing to tell you about is the way Roman Numeral work.

So, Roman Numeral are combination different letters.

When we put those letters together, they tell us, or they represent different numbers.

You might have one letter on its own that could represent a number.

You might have two together, three together, five together, sometimes even more than that for the larger numbers.

And depending on where you place those letters, helps you to represent different numbers.

So the first thing I have to show you is the numbers one, five, and 10.

And the reason that we show those first is that actually you can work out all of the other numbers between one and 10 using those three symbols.

So, the letter that corresponds to the number one is the letter I.

Sometimes you see it with the two lines going horizontally at the top, sometimes you just see as a straight vertical line down, either way, the letter I represents the number one.

The next time I'm going to tell you about is the number five.

The number five is represented with the letter V and the V stands on its own and that means five.

And the next number is the number 10.

The number 10 is represented by the letter X.

So one X on its own means just 10.

Using just those three symbols, we can actually work out all of the other Roman Numerals and you can see the number twos being done for you there.

Because actually, if one I means one, then two Is must mean two.

So then number three, how are we going to write the number three, three seconds to write it down.

We're going to have three Is next to each other.

Three Is next to each other represents the number three.

Now let's think about the number four.

And this is where my next role of Roman Numerals comes in.

Because you might have assumed that in order to write the number four, we would write four Is all in the line next to each other, just like we did from the number three.

But one of the morals of Roman Numerals is that you cannot write the same letter more than three times in a row.

If you're thinking about doing that, you need to find another way of representing that number.

So really important rule, we don't write the same letter more than three times in a row for any one number.

So in order to write the number four, we need to think about its relationship with the number five.

So let's think about that.

The number four comes before five, the number four is five minus one, and that is exactly how we represent the number four using Roman Numerals.

We use the number five, but just before the number five, we placed the number one, because what that represents is five minus one.

If the number or if the letter comes before another letter we're minusing it.

And so in this case, we're doing five minus one.

I sometimes like to think of this as the one before five.

I before V means the one before five and of course that's four.

And actually just helps us with writing in number six, because if a letter comes before the number we subtract it.

But if a letter comes after a number, we add it on.

So in this case, I've got V plus one so V plus one is equal to six.

So you know, that five plus one is equal to six and placing I next to the V, demonstrates that this is the number that comes after the five so adding on.

So if VI means six, then creating seven is actually fairly straightforward.

We want a V and then we want two Is because that means, five plus one plus one, which is equal to seven.

So creating the number eight, three seconds, how would we do it? So hopefully you've seen, you'd need your V and then you'd need three Is straight after it.

Now the number nine is a little bit harder because remember our rule, we can't put the same symbol more than three times in a row.

So I can't use VIIII because that breaks that Roman Numeral rule.

So instead I'm referring to the 10, how would I demonstrate in the same way that I did the four, how would I demonstrate the one before 10 or 10 minus one? Three seconds to work it out.

So I hope that you've seen in order to create the number nine, I would need to use an I before the X, because placing the I before the X symbolises to me that it's the one before 10 or 10 minus one.

Remember whenever you place a letter before another letter, we are subtracting it when those letters come together.

So there you have it that is the full range of numbers between one and 10 written in Roman Numerals.

And the great thing about this is that if you know those numbers, you can actually work out a range of other numbers using the same system, using the same rules.

Let's have a look.

So, what I'd like you to do is have a little practise of this before we move on to the next set of numbers, up to 100.

There are on your left hand side of the screen, there are some Roman Numeral that have been written and on your right hand side, you've got the Arabic Numerals that you'll be more familiar with.

I'd like you to spend a couple of minutes matching each of the Roman Numerals to the Arabic Numerals.

Pause the video to complete your task and resume it once you're finished? Okay, let's have a look at matching these up together.

So the first Roman Numeral that we're matching up has two letter Is, and we know one I means one so two of them must mean two so this number here means two.

The next number has an I then an X and reminding ourselves again, if we put a letter before another letter, then that shows us that we're subtracting it from that letter so here we've got 10 minus one, which is equivalent to nine.

I always like thinking to ask the number before 10 that means nine.

The V symbolises the number five, and then the VII symbolises a five plus a one plus a one, which is equivalent to seven.

The X means 10, and of course the I as we reminded ourselves earlier on means the number one.

So there you go, you've matched up all of the Roman Numerals on the screen with the Arabic numerals that correspond.

So let's move on and look at the Roman Numerals up to 100.

And actually this is a really useful bit of information in the speech bubble here.

It says that, only five symbols are needed to know all the Roman Numerals up to 10.

Three of those symbols we've already looked at.

These are the five symbols you need to know.

So we know already that I equals one.

We know that V equals five, and we know that X equals 10.

These are the two new ones for us to memorise we need to remember that L equals 50 and C equals 100.

A top tip for remembering the C equals 100 if I always think back to the word sent, which reminds myself that we're talking about 100, because cent to me is 100 if you think about centimetres and the number of centimetres in the metre, there are 100.

If you think about centipede, centipedes have 100 legs.

So the word cent begins with the letter C and that reminds me that the C stands for 100.

So using that information, we're going to have a go at identifying the Roman Numerals for each of the Arabic Numerals on the screen here.

I'm going to hide my picture and you can see the Roman Numerals really clearly.

And we're going to start with the number 52.

So we're going to identify how to write the number 52 using Roman Numerals and using the information that we've got.

The first thing I'm going to do is partition out the number 52.

This is the best way to ensure that we get all of the information.

So I know the 52 is made up of a 50 and a two.

So all I need to do is work out the code, which letters represent 50, and which represents two.

What I know straight away, the L represents 50 so I'm starting with an L.

And in order to make the number two, I remind myself I'm going to use two of these Is.

So in order to make 52, I use the symbols LII.

Similarly let's look at creating the number 37 so again, partitioning out the number because that's a really handy way of identifying which symbols are going to be needed.

So I can't see anything here that represents 30, but I can make a 30 using my tens.

How many tens will I need to make 30? Well, I need three.

So here I go, I've got my 30, and then I need to make a seven.

Well, I don't have anything that represents seven directly, but if I use my V to represent five and II next to it, that shows me seven.

So this part here shows me 30, and this part here shows me seven.

Again using that same partitioning strategy for 75.

I need to, first of all, represent 70, then I need to represent five.

Nothing on here shows me 70, but I can make 70 with a 50 and two tens.

So I'm going to create my 50, my two tens come after the 50 to show that I'm adding them on.

And then my five is just my V, LXXV.

91, 91 is a slightly more challenging one because I've got to make 90 first of all and then I've got to make one.

Let me remind you of what we're not allowed to do.

What I can't do is use an L and then four Xs afterwards, because remembering back to our number one rule, we can't use a symbol, a letter more than three times in a row.

So I need to create the number 90 in another way, and actually I'm going to use this symbol for 100.

And I'm also going to use the symbol for 10, because what I'd like to do is demonstrate 100 minus 10 I know that means 90.

So what I'm going to do is, I'm going to put the X before the C and reminding myself that what that means is 100 minus 10 or the 10 before 100, which is 90.

And then to create the one, I just use my letter I, XCI.

So you can see that we've managed to create all of the different Roman Numerals to match up on correspond with the Arabic Numerals.

Some top tips to remember firstly, partition your number, break it up, so you're representing each of the different parts intern.

Represent the first part first and then the second parts.

Another top tip is to remember that number one rule, don't use the symbols more than three times.

If you're having to do that, think of another way that you'd be able to represent that number.

Let's have a go at one for you to have a try it yourself.

So here, I've got four numbers, 12, 45, 78 and 93.

Can you represent those numbers using the Roman Numerals on your screen.

Pause the video to complete your task and resume it once you're finished.

Okay, let's have a look at this together.

So first of all, we're creating the number 12.

Well, I can see that in order to create 12, I'm partitioning out my number.

I've got a 10 and I've got two.

To create my 10 I'm using my X , and to create my two, I'm using two of my Is.

XII is the symbol for 12 and you might notice that it's quite familiar.

And that's because you'll often see at the top of the clocks or the watch faces that you might have that you use Roman Numerals because of course, 12 is right at the very top of our clocks.

45 partitioning out 45, first of all.

So we need to represent 40 and we need to represent five.

Well to create 40, I could try and do X, X, X, X, but that would break the rule.

The rule says, I can only use a symbol, the same symbol at three times maximum in a row.

So instead I'm going to use my 50 symbols help me out here.

And I'm going to actually put my X, which means 10 before the L.

And that represents 50 minus 10 because the 10 comes before it.

And of course that means 40.

And then my five is represented with my B.

78, again, partitioning out because I'm always dealing with the first part first, the tens.

So in order to create my 70, I'm using my L for 50 plus two of my tens, which are Xs and to create my eights.

I've got a VIII, so that's one of the longer numbers that you can see we've used.

One, two, three, four, five, six, seven different symbols to create the number 78.

93, remembering that I can't use a symbol more than three times.

So to create my 90, I'm going to have to use my 100 and my 10 so the 10 comes before the 100, and then I've got my three Is in a row just like that.

How did you get on? Give yourself a tick if he got those ones correct.

The last part of the lesson today is looking at some Roman numeral sequences.

So what we're going to have a go at doing is identifying the end of the sequence, using the different Roman Numerals that we've learned about between one and 100 today.

So let me show you how I would tackle this first of all.

Well, the first thing I want to do is work out what the sequence is going up in and what I'm going to do to help me out here is convert each of the Roman Numerals into Arabic Numerals.

So I've got here, my I represents one, then I've got a three, then I've got a five.

I can already see straight away, that these numbers are increasing by two each time.

So what I'm going to want to represent next is a seven and then a nine.

Then my task is to create the Roman Numerous represent this.

So I know seven is going to be represented as VII and a nine reminding myself that it's the one before the 10 is represented with an I and an X just like that.

Let's have a look at the next one.

I'm going to give you five seconds to see if you can work out what each of the numbers are in this Roman Numeral sequence.

Okay, I'm converting them again to Arabic Numerals so I helped myself out immediately here.

I've got an X and V, I know that's a 10 and a five which is 15.

I've got three Xs in a row, which must be 30.

And then I've got an X an L and a V.

So I'm reminding myself that the L means 50.

And when you put an X before, it's the Xs smaller so therefore that must mean the 10 that comes before 50 or 50 minus 10, which is 40 and so that must be 40 and then five.

So I can see straight away here that my numbers are going up in 15 and adding 15 each time.

So 45 plus 15 is equal to 60, how do I create the number 60 using Roman Numerals? Five seconds to work it out.

Okay, so hopefully you've used that L again, that's 50, but because I'm making 60, I need to add on a 10.

So I'm adding on my X to the end.

There we go we've completed our Roman Numeral sequences.

Now it's your turn to have a go, can you complete the Roman Numeral patterns using the same strategy that I've used.

Convert each of those numbers to Arabic Numerals fast, workouts, how they're increasing or in some cases decreasing, and then identify what comes next in the sequence.

Pause the video now to complete your task and resume it once you're finished.

Okay, let's have a look at the answers together and see how you got on.

So converting my Roman Numerals into Arabic numerals firs of all, I know that XX must mean 20, XL must be 40 and LX must be 60.

So we're increasing by 20 each time that means I want to represent the number 80 next.

In order to represent the number 80, I'm going to use my 50, which is L and then 60, 70, 80, and adding on three of my Xs, three of my tens to represent 80.

Okay, the next one that's have a peak.

So I've got an XIV that represents a 10 plus a four, which is 14.

The next one is XII, which represents 12 and then I've got 10 here.

This sequence is decreasing, it's going down by two each time.

So I'm going to need to represent eight and six in the next few terms in my sequence.

So an eight is representatives VIII, and a six is VI.

Give yourself a tick if you've got those ones correct.

And now it's time for independent task.

What I'd like you to do is work through the questions on the screen that you can see here.

The first asks you to write the numbers that we've got an Arabic Numerals in Roman Numerals, then you're going to have to write the Roman Numerals in Arabic Numerals.

And then you've got question three and four, which asked you to complete the sequence.

Pause the video now to complete your task and resume it once you're finished.

Okay, how did you get on? Here are the answers on your screen, spend a bit of time marking your answers.

And if you made a mistake, go back and have a look see whether one of the mistakes that you've made has been breaking that rule, that you're not allowed to use the symbol more than three times in a row, because often that's where we make the most of our mistakes when we're creating Roman numerals.

So Mark your answers now, pause the video and then resume it once you're finished.

So if you'd like to share, please ask your parent or carer to share your work on Twitter, tagging at OakNational and hashtag LearnwithOak.

Now it's time to complete your quiz.

Thank you so much for joining me for our math lesson today on Roman Numerals.

I hope you've managed to crack the Roman Numeral code.

Do join me again soon, bye bye.