Page 26 - Maths Skill - 3

24 Maths

We can use combination of these seven letters to make different numbers but certain
rules are to be followed:

Rule 1: I, X, C and M can be repeated up to three times. The number so formed is their
sum.
For example, III = 1 + 1 + 1 = 3 XX = 10 + 10 = 20

Rule 2: V, L and D are never repeated.
For example, we cannot write 10 as VV. We write 10 as X.

Rule 3: When we write a smaller Roman numeral after a greater Roman numeral,
their values are added.
For example, VI = 5 + 1 = 6 XI = 10 + 1 = 11

XII = 10 + 1 + 1 = 12 XV = 10 + 5 = 15

Rule 4: When we write a smaller Roman numeral before a greater Roman numeral,
their values are subtracted.
For example, IV = 5 – 1 = 4

IX = 10 – 1 = 9 Fact-o-meter
Rule 5: A smaller numeral between two
greater numerals gets subtracted � There is no symbol for zero in
from the numeral on its right. Roman number system.
� There is no concept of place
For example, XIV = 10 + (5 – 1) = 14 value in Roman number system.

� 4 = IIII 7 4 = IV 3
XIX = 10 + (10 – 1) = 19

Some Roman numbers with their corresponding Hindu-Arabic numbers are given below.

1 2 3 4 5 6 7 8 9 10
I II III IV V VI VII VIII IX X

11 12 13 14 15 16 17 18 19 20
XI XII XIII XIV XV XVI XVII XVIII XIX XX

Exercise 2.9

1. Write the following Roman numbers in Hindu-Arabic system.
(a) IX (b) XII (c) XIV (d) XIX

(e) XX (f) XV (g) IV (h) VIII
2. Write the following numbers using Roman numerals.

(a) 7 (b) 11 (c) 13 (d) 18
(e) 17 (f) 20 (g) 9 (h) 15