Page 26 - ICSE Math 5

As 4 < 5 and 4 = 5 – 1 = V – I = IV.
Therefore, 4 is written as IV in the Roman numeral system.
Numbers 6, 7 and 8 are written as VI, VII and VIII, respectively. Again 9 cannot be written as VIIII
since I cannot be repeated more than thrice.

As 9 < 10 and 9 = 10 – 1 = X – I = IX, therefore, 9 is written as IX.
Similarly, 40 = 50 – 10 = L – X = XL and 90 = 100 – 10 = C – X = XC.

To write a large Hindu-Arabic numeral in the Roman Mental Maths
numeral system, write the expanded form of the given
Fill in the blanks.
number and then write the symbols in combination.
(a) 366 = CC ____ XVI
Example 1: Write 428 in the Roman numeral system. (b) 524 = DXX ____
Solution: 428 = 400 + 20 + 8 (c) CCLVII = 200 + ____ + 7

= CD + XX + VIII = CDXXVIII (d) CMII = ____ + 2

Addition and Subtraction of Roman Numerals

To add or subtract Roman numerals, we follow the given steps.
• Change the number into Hindu-Arabic numbers.

• Add or subtract accordingly.
• Convert the answer into Roman numeral.
Example 2: Add XLV and LXIII. Example 3: Subtract CLXXIV from CCXCVI.

Solution: XLV = 45 Solution: CCXCVI = 296
LXIII = 63 CLXXIV = 174
45 + 63 = 108 = CVIII 296 – 174 = 122 = CXXII

So, XLV + LXIII = CVIII So, CCXCVI – CLXXIV = CXXII

Exercise

1. Fill in the blanks using the Hindu-Arabic numerals.
(a) XXVII = ________ (b) DXLII = ________ (c) LXXVI = ________

(d) MMM = ________ (e) LIX = ________ (f) CDXLV = ________

2. Fill in the blanks using the Roman numerals.
(a) 187 = ________ (b) 345 = ________ (c) 949 = ________

(d) 736 = ________ (e) 67 = ________ (f) 222 = ________
3. Add the following and write the sum using Roman numerals.

(a) CIV + XC (b) MM + CM (c) D + CC (d) LXXV + CIX

4. Subtract the following and write the difference using Roman numerals.
(a) M – CMXX (b) XXIV – XVII (c) DCC – XXVII (d) CCXC – LXV

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