## What are Roman Numerals

Roman numerals are a different system of writing numbers. Instead of using the digits of 1, 2, 3, 4, 5, 6, 7, 8, 9 or 0, Roman numerals use the capital letters of the alphabet: I, V, X, L, C, D and M.

To write larger numbers, numerals can be added by writing them next each other.

Roman numerals to 10 are written using the three numerals of I, V and X.

I is the first Roman numeral. I is the roman numeral for 1.

We can add two ones together to make 2. We add numerals by writing them next to each other.

II is made from two I numerals. II means 1 + 1.

II is worth 2.

2 is written as II in Roman numerals.

We can add up to three of each numeral.

We can add three I numerals to make III.

III means 1 + 1 + 1.

3 is written as III in Roman numerals.

We can only use three Roman numerals together at once.

We have already used three I numerals to make III.

To make larger numbers, we need to use the numeral of V.

V is the Roman numeral for 5.

So far we have:

I = 1

II = 2

III = 3

V = 5

4 is written a little differently in Roman numerals.

We are not supposed to write more than 3 of the same numeral together. We can’t write IIII for 4 because this contains more than three I numerals.

Instead we use the fact that 4 is one less than 5.

We can write 4 as one less than five.

We write 4 as one before five. 1 is written as ‘I’ and 5 is written as ‘V’.

To write 1 before 5, we write I before V.

4 is written as IV in Roman numerals.

Here is a chart showing the Roman numerals to 5.

We have I for 1, II for 2, III for 3, IV for 4 and V for 5.

To make the numbers larger than 5 using Roman numerals, we count on in ones from five.

5 is written using the numeral of V.

We can count on from five using the numeral of I. We can use up to three I numerals at once.

6 is one more than five. To write one more than five, we write an I after a V.

6 is Roman numerals is VI. VI is V + I, which is 5 + 1.

7 is two more than five. To write two more than five, we write two I numerals after a V numeral.

7 in Roman numerals is VII. VII is V + I + I, which is 5 + 1 + 1.

8 is three more than five. To write three more than five, we write three I numerals after the V numeral.

8 in Roman numerals is VIII. VIII is V + I + I + I, which is 5 + 1 + 1 + 1.

The Roman numeral for 10 is X.

In the same way that we wrote 4 as IV, we write 9 as IX.

We cannot write VIIII for 9 because it would mean using four I numerals. We are only allowed to use three at most.

We write 9 in Roman numerals as IX, which is an I before an X. 1 before 10 is 9.

Both 4 and 9 are different to the other Roman numerals because they have an I before another numeral.

4 is one before 5 and so is written IV.

9 is one before 10 and so is written IX.

These are the only numbers in the list of Roman numerals to 10 that behave like this.

When teaching Roman numerals, 4 and 9 are most commonly written incorrectly.

Some students can think that IV is 1 + 5, rather than reading it as 1 before 5.

It is important to show the difference between 4 and 6.

4 is IV and 6 is VI. If a smaller numeral is written **before** a larger value numeral then we subtract the smaller numeral away from the larger numeral.

There is no Roman numeral for zero.