Try the Roman Numeral Challenge.
Roman numerals are expressed by letters of the alphabet:
There are four basic principles for reading and writing Roman numerals:
- 1. A letter repeats its value that many times (XXX = 30, CC = 200, etc.). A letter can only be repeated three times.
- 2. If one or more letters are placed after another letter of greater value, add that amount. 3. If a letter is placed before another letter of greater value, subtract that amount.
VI = 6 (5 + 1 = 6)
LXX = 70 (50 + 10 + 10 = 70)
MCC = 1200 (1000 + 100 + 100 = 1200)
IV = 4 (5 – 1 = 4)
XC = 90 (100 – 10 = 90)
CM = 900 (1000 – 100 = 900)
Several rules apply for subtracting amounts from Roman numerals:
- a. Only subtract powers of ten (I, X, or C, but not V or L)
For 95, do NOT write VC (100 – 5).
DO write XCV (XC + V or 90 + 5)
- b. Only subtract one number from another.
For 13, do NOT write IIXV (15 – 1 - 1).
DO write XIII (X + I + I + I or 10 + 3)
- c. Do not subtract a number from one that is more than 10 times greater (that is, you can subtract 1 from 10 [IX] but not 1 from 20—there is no such number as IXX.)
For 99, do NOT write IC (C – I or 100 - 1).
DO write XCIX (XC + IX or 90 + 9)
- 4. A bar placed on top of a letter or string of letters increases the numeral's value by 1,000 times.
XV = 15, = 15,000
|One ||I ||Eleven ||XI ||Thirty ||XXX|
|Two ||II ||Twelve ||XII ||Forty ||XL|
|Three ||III ||Thirteen ||XIII ||Fifty ||L|
|Four ||IV ||Fourteen ||XIV ||Sixty ||LX|
|Five ||V ||Fifteen ||XV ||Seventy ||LXX|
|Six ||VI ||Sixteen ||XVI ||Eighty ||LXXX|
|Seven ||VII ||Seventeen ||XVII ||Ninety ||XC|
|Eight ||VIII ||Eighteen ||XVIII ||One hundred ||C|
|Nine ||IX ||Nineteen ||XIX ||Five hundred ||D|
|Ten ||X ||Twenty ||XX ||One thousand ||M|
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