Writing Roman Numerals

A quick lesson on how to write like the Romans for grade schoolers

A Roman numeral is part of the number system of ancient Rome that uses certain letters from the alphabet. Each letter is assigned a particular value, and the numbers are formed by combining the symbols together and adding or subtracting the values. Here, Jethro Dionisio, a math tutor from AHEAD Interactive, gives a quick lesson on Roman Numerals. AHEAD Interactive provides real-time, face-to-face online tutorials, including interactive Math tutorials.

To make Roman numerals, the following letters are used to represent the following values:

I – 1

V – 5

X – 10

L – 50

C – 100

D – 500

M – 1000

The first twenty Roman numerals are:

I – 1

II – 2

III – 3

IV – 4

V – 5

VI – 6

VII – 7

VIII – 8

IX – 9

X – 10

XI – 11

XII – 12

XIII – 13

XIV – 14

XV – 15

XVI – 16

XVII – 17

XVIII – 18

XIX – 19

XX – 20

There are several rules that should be remembered when writing Roman numerals. These rules are:

1. Certain Roman numerals that are grouped together can be written in succession for up to three times only. These are the letters I, X, C and M.

Ex. III – 3

XXX – 30

CCC – 300

MMM – 3000

1. The letters D, L, and V cannot be written consecutively). For example, you cannot write LL to represent 100. Instead, use the letter C, which stands for 100.

Ex. DLV – 555

Because D (500) + L (50) + V (5) = 555

1. If a letter with a smaller value is placed after a letter with a larger value, you add the values.

Ex. XII – 12

Because X (10) + I (1) + I (1) = XII (12)

1. If a letter with a smaller value is placed before a letter with the larger value, you subtract the smaller number from the larger number.

Ex. XL – 40

X (10) has a smaller value than L (50), so you should subtract: L (50) – X (10) = XL (40)

1. Only one number can be subtracted from another. For example, instead of writing 19 in Roman numerals as IXX (as in 20 minus 1), you should:

Ex. XIX – 19

Because X (10) + [X (10) – I (1)] = XIX (19)

1. The Roman numeral I can be subtracted from V and X only.

Ex. IV – 4

Because V(5) – I (1) = IV (4)

IX – 9

Because X (10) – I (1) = IX (9)

1. The Roman numeral X can be subtracted from L and C only.

Ex. XLI – 41

Because [L (50) – X (10)] + I (1) = XLI (41)

XC – 90

Because C (100) – X (10) = XC

1. The Roman numeral C can be subtracted from D and M only.

Ex. CD – 400

Because D (500) – C (100) = CD (400)

MCMXCVII – 1997

Because M (1000) + [M (1000) – C (100)] = MCM (1900)

C (100) – X (10) = XC (90)

V (5) + I (1) + I (1) = VII (7)

Put together MCM (1900) + XC (90) + VII (7) = MCMXCVII (1997)

1. The values V, L, and D are never subtracted.
2. Never subtract a number that is more than 10 times greater. For example, you can subtract I (1) from X (10), but you cannot subtract I (1) from XX (20).

Ex. XCIX – 99

Because C (100) – X (10) = XC (90), and X (10) – I (1) = 9

Put together XC (90) + IX (9) = XCIX (99)

If you’re having problems understanding Roman Numerals, then you might want to try getting online Math tutorials. For more information on online academic tutorials, e-mail aisupport@ahead.edu.ph or click here.