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.