The ancient Romans made up one of the first ways of counting over three thousand years ago.
They didn't use digits like 1, 2, and 3. Instead, they used Roman numerals, like I, V, and X.
Roman numerals are made up of seven symbols, each with a different value.
You can use this sentence to help you remember their value:
My Dear Cat Loves Xtra Vanilla Ice-cream
We put the symbols together in a certain order to make a number.
Rule 1: When a smaller symbol is after a greater symbol, it's added.
Rule 2: If a symbol comes after itself, it's added.
This shows the Roman numeral for 160:
Rule 3: When a smaller symbol appears before a greater symbol, it is subtracted.
For example:
Here's the Roman numeral for 40:
The way we write 90 in Roman numeral is like this:
Rule 4: The symbols I, X, and C cannot appear more than three times in a row.
For example, we don't write 40 as XXXX, we write it as XL.
400 isn't CCCC, it's CD.
Rule 5: The symbols V, L, and D are never repeated.
So, we don't write VVV to make 15. Instead, we write 15 as XV.
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. 👏
Let's learn with some practice.
What number is CDLXIV?
First, write the value of each letter.
Next, check if there are smaller values that come before larger values.
If you find any, then start subtracting.
We see that there are two values that we need to subtract.
The value of CDLXIV is 464. ✅
Awesome.
Now, let's try doing the opposite.
To convert a basic number into a Roman numeral, break the number into thousands, hundreds, tens, and ones. Then write the letters for each value.
Write 1996 in Roman numerals?
First, break down the number into Thousands, Hundreds, Tens, and Ones.
Then, write down each value as a Roman numeral.
Lastly, combine all the letters.
Now, we see that 1996 in Roman numeral is MCMXCVI. ✅
Great job learning about Roman numerals.
Tip: It's Roman numerals, not Roman Numerals.
Try the practice to see if you got it.