# Class 6 Maths - Knowing Our Numbers (Roman Numbers)

๐ Around the 3rd century BCE, Romans developed their own number system for counting.

๐ Roman Numerals used symbols to represent numbers such as

Roman Numeral Hindu-Arabic Numeral

I 1

V

X 10

L 50

C 100

D 500

M 1000

๐ Repetition of Roman Numerals means addition but using the following rules

- Only I, X, C, M may be repeated

- V, L, D are never repeated

- No symbol can be repeated more than 3 times.

e.g.  III = 1 + 1 + 1 = 3,

VI = 5 + 1 = 6,

VII = 5 + 1 + 1 = 7

XX = 10 + 10 = 20

XXII = 10 + 10 + 1 + 1 = 22

CC = 100 + 100 = 200

CX = 100 + 10  = 110

๐ Smaller numerals written to the left of a larger numeral means subtraction.

e.g. IV = (-1)5 = 5 -1 = 4

XC = (-10)100 = 100 - 10 = 90

Following rules are followed in subtraction.

- V, L, D are never repeated.

- I can be subtracted from V and X only

e.g. IX = 9, IL = Not Valid

- X can only be subtracted from L and C

e.g. XL = (-10)50 = 50 - 10 = 40

- C can only be subtracted from D and M only

Q1: Write each of the following Roman numerals as Hindu-Arabic numerals:

(a) II

(b) XX

(c) XV

(d) CC

(e) CD

(f) XC

(a) II = 1 + 1 = 2

(b) XX = 10 + 10 = 20

(c) XV = 10 + 5 = 15

(d) CC = 100 + 100 = 200

(e) CD = -100 + 500 = 500 - 100 = 400

(f) XC = -10 + 100 = 100 - 10 = 90

Q2: Express each of the following as a Roman numeral

(a) 8

(b) 14

(c) 195

(d) 341

(e) 99

(a) 8 = 5 + 1 + 1 + 1 = VIII

(b) 14 = 10 + (-1) + 5 = XIV

(c) 195 = 100 + 90 + 5

= C + XC + V = CXCV

(d) 341 = 300 + 40 + 1

= 100 + 100 + 100 + 50 - 10 + 1

= C + C + C + L - X + I

= CCCXLI

(e) 99 = 90 + 9 = 100 - 10 + 10 -1

= XC + IX = XCIX