Page 10 - SM Class 4 Inner.cdr

Rule 2 : When a digit of lower value is written to the right or after a digit of higher
a.
value, the values of all the digits are added. As :
VI = 5 + 1 = 6 XV = 10 + 5 = 15
VII = 5 + 1 + 1 = 7 XVI = 10 + 5 + 1 = 16
VIII = 5 + 1 + 1 + 1 = 8 LX = 50 + 10 = 60
XI = 10 + 1 = 11 LXV = 50 + 10 + 5 = 65
XII = 10 + 1 + 1 = 12
b. Value of similar digits are also added as indicated in rule 1.
III = 1 + 1 + 1 = 3 XXX = 10 + 10 + 10 = 30
XX = 10 + 10 = 20

Rule 3 : When a digit of lower value is written to the left or before a digit of higher
value, then the value of the lower digit is subtracted from the value of the digit of
higher value. As :
IV = 5 – 1 = 4 XIX = 10 + (10 – 1) = 19
IX = 10 – 1 = 9 XXIX = 10 + 10 + (10 – 1) = 29
XL = 50 – 10 = 40 XLV = (50 – 10) + 5 = 45
XIV = 10 + (5 – 1) = 14 CLIX = 100 + 50 + (10 – 1) = 159
However, V is never written to the left of X.

Rule 4 : a. If we have to write the numbers beyond 10 we should write the number
10 or groups of number 10 and then number 5 or 1 as the case may be. Then these
numbers are used to change to the corresponding Roman numerals. As :
12 = 10 + 2 = 10 + 1 + 1 = XII
20 = 10 + 10 = XX
22 = 10 + 10 + 1 + 1 = XXII
26 = 10 + 10 + 5 + 1 = XXVI
39 = 10 + 10 + 10 + (10 – 1) = XXXIX
37 = 10 + 10 + 10 + 5 + 1 + 1 = XXXVII
b. According to this pattern, numbers higher than number 40 are also formed :
43 = (50 – 10) + 1 + 1 + 1 = XLIII
56 = 50 + 5 + 1 = LVI
159 = 100 + 50 + (10 – 1) = CLIX
1238 = 1000 + 100 + 100 + 10 + 10 + 10 + 5 + 1 + 1 + 1 = MCCXXXVIII, (M=1000)

Rule 5 : If a horizontal line is drawn over the symbols or digits of Roman
numerals, then the value of the numerals becomes 1000 time. As :
XV = 15 but XV = 15000, CLV = 155 but CLV = 155000

E xercise 1.1

1. Write the Roman Numerals for the following numbers :

a. 13 = ________ b. 14 = ________ c. 18 = ________
d. 26 = ________ e. 39 = ________ f. 42 = ________
g. 61 = ________ h. 245 = ________ i. 217 = ________
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Mathematics In Focus - 4