Roman Numerals I, V, X, L, C, D, M

🤓 Look at this clock. It uses some **symbols **to show the numbers 1-12.

Do you know what these numbers are called? 🤔

Numbers such as I, VI and IX are called **Roman numbers **(or **Roman numerals**).

👉 These numbers were invented by the **ancient Romans **almost 3,000 years ago! They used symbols to write numbers.

In this lesson, let's learn how to read and write Roman numbers. 🤗

Here's how you count from 1 to 3 in Roman numerals:

I = 1

II = 2

III = 3

Easy so far right?

Can you guess what 4 is? You may think it's 4 I's, but it's actually:

IV = 4

What is that **V **symbol? 🤔

In Roman numerals, **V **is the symbol for 5.

V = 5

In Roman numerals, you never write more than 3 of the same symbol in a row.

That's why after III comes IV.

So what do you think comes after V? 🤔

We add another I.

VI = 6

We can add one more **I** to get 7.

VII = 7

In Roman numerals, it's ok to have 3 of any symbol in a row, but no more. So after 7 comes:

VIII = 8

Now what do we do? We can't add another I. So we need to use a new bigger symbol:

X = 10

To make 9, we take away 1 from 10:

IX = 9

**Remember:** when we write **I before **a bigger symbol like V or X, we take away from that number.

Great job learning to count from I to X in Roman numerals!

To count to 10, you've had to use 3 of the symbols that make up Roman numerals: **I, V, X.**

Now let's learn the other 4 symbols: **L, C, D, **and **M.**

😃 Roman numerals are all made up of **seven ****symbols.**

You've learned I, V, and X. Here are the 4 bigger symbols:

L= 50

C= 100

**Tip:** a **c****entury **is 100 years. It starts with c.

D= 500

M= 1,000

**Tip:** a **m****illennium **is 1,000 years! It starts with m.

**TIP!**

😎 You can **use this sentence **to help you remember the order:

✅ All roman numerals are **combinations **of the basic 7 symbols.

These combinations follow **four important rules:**

**Rule 1:**** **When a smaller symbol is **after** a greater symbol, it's **added.**

For example,

VI=5+1= 6

**Rule 2:** If a symbol comes after itself, it's added.

XX=10+10= 20

CCLX=100+100+50+10= 260

**Rule 3: **When a smaller symbol appears **before **a greater symbol, it is **subtracted.**

For example,

IX=10-1= 9

XL=50-10= 40

CM=1000-100= 900

**Rule 4: **The same symbol **cannot be used more than three times **in a row.

For example,

XXX=10+10+10= 30,but40is not XXXX.

CCC=100+100+100= 300,but400is not CCCC.

🤗 Let's now use these rules to learn some basic roman numerals.

1 =I

2 =1+1=II

3 =1+1+1=III

4 =5-1=IV

5 =V

6 =5+1=VI

7 =5+1+1=VII

8 =5+1+1+1=VIII

9 =10-1=IX

10 =X

20 =10+10=XX

30 =10+10+10=XXX

40 =50-10=XL

50 =L

60 =50+10=LX

70 =50+10+10=LXX

80 =50+10+10+10=LXXX

90 =100-10=XC

100 =C

200 =100+100=CC

300 =100+100+100=CCC

400 =500-100=CD

500 =D

600 =500+100=DC

700 =500+100+100=DCC

800 =500+100+100+100=DCCC

900 =1000-100=CM

1000 =M

Great work! 👏

Now, let's learn how to read and write other roman numerals.

👉 Look at this roman numeral.

CDLXIV

How will you convert it into digits? 🤔

That's right! 😎

**To convert a roman numeral into digits,** find the value of each symbol in it, and then add or subtract these values.

Let's try to do that now!

✅ First, let's **find the value **of each symbol.

✅ Now, let's see if there are any **smaller symbols appearing before bigger symbols.**

This is because we need to **subtract **those values (**Rule 3**)!

Here is **Rule 3 **one more time:

Rule 3:When a smaller symbol appears before a greater symbol, it is subtracted.

✅ Now, let's add/subtract the values.

CDLXIV= (500-100) + (50+10) + (5-1)

= 400 + 60 + 4

🤓 So, what's the value of this roman numeral?

Correct! 🤗

CDLXIV= 464

Awesome! 👌

Let's try one more example.

👉 Convert this roman numeral to digits.

MDCXLI

Let's do it! 😃

How do we start? 🤔

✅ First, we **find the values **of all the symbols.

✅ Next, we find any smaller symbols that appear before bigger symbols.

✅ Now, let's add/subtract the values.

MDCXLI=1000+ (500+100) + (50-10) +1

= 1000 + 600 + 40 + 1

So, the value of this roman numeral is:

MDCXLI= 1,641

Perfect! 😎

👉 Now, let's try converting this number into a roman numeral.

2,342

How will you do it? 🤔

Very good! 😎

**To convert a number into a roman numeral,** split the number into the values of I, V, X, L, C, D, M.

Let's try!

2,342 = 2000 + 300 + 40 + 2

So, what is the answer? 😃

2,342 =MMCCCXLII

Nice job! 👏

Let's try one last example.

👉 Convert this number into a roman numeral.

978

Let's do it!

978 = 900 + 70 + 8

So, what's the answer? 🤓

978 =CMLXXXVIII

You got it! 🤗

You did great learning about Roman numerals! 👏 Now try the practice questions.

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