Arabic and Roman Numerals
The following table lists the basic symbols of the Roman numeral system and their Arabic equivalents.
Roman numeral |
Arabic equivalent |
I |
1 |
V |
5 |
X |
10 |
L |
50 |
C |
100 |
D |
500 |
M |
1000 |
Counting to ten in Roman numerals
I |
II |
III |
IV |
V |
VI |
VII |
VIII |
IX |
X |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
Look at the Roman numerals for 4 (IV) and 9 (IX). If the Roman numeral for 3 is III, why isn’t 4 = IIII. This is because the Roman numeral system uses something called subtraction notation. Using subtraction notation, instead of writing 4 as four lines, we write one in front of V (IV) indicating 5 - 1 which equals 4. Under this subtraction notation, a given symbol can only be written 3 times in a row. After three times we express the number as an amount subtracted from the next highest symbol. Therefore, we have:
I = 1 |
II = 2 |
III = 3 |
IV = 4 |
5-1 = 4 |
V = 5 |
V is never written more than once because VV would equal ten, |
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VI = 6 |
VII = 7 |
VIII = 8 |
IX = 9 |
10-1 = 9 |
X = 10 |
XX = 20 |
XXX = 30 |
XL = 40 |
50-10 = 40 |
L = 50 |
Like V, L is never written more than once since LL=100 which is |
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LX = 60 |
LXX = 70 |
LXXX = 80 |
XC = 90 |
100-10 = 90 |
C = 100 |
CC = 200 |
CCC = 300 |
CD=400 |
500-100 |
Roman Numeral Pattern
Using this method of subtraction notation, we can construct larger numbers without having to write out so many digits.
4 =IV |
40 = XL |
400 = CD |
9 = IX |
90 = XC |
900 = CM |
Based on the pattern above, the Roman numeral for 95 would be written XCV, not VC since V cannot come before C. This is also true because we want the numbers following 95 to begin the same way with an XC.
Practice 1: Write the following Roman numerals as Arabic numerals.
1. MCMXXIII |
2. CCCXII |
3. XLIX |
4. MMCCLVII |
5. XXXIX |
6. CMLXVII |
7. DXXVIII |
8. CDLI |
9. III |
10. CXXIV |
11. IV |
12. XL |
Practice 2: Write the following Arabic numerals as Roman numerals.
1. 1,623 |
2. 814 |
3. 25 |
4. 59 |
5. 592 |
6. 2,487 |
7. 96 |
8. 16 |
9. 701 |
10. 237 |
11. 38 |
12. 6 |
