Year 4A · Grade 6: Roman Numerals and Number Words
Review I through X from Year 3, then read the larger signs through M and count to twenty.
What to notice
- Roman numerals
- cardinals
- ordinals
Explanation
Roman numerals build from seven signs: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. A smaller sign before a larger one subtracts: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400, and CM is 900. A smaller sign after adds: VI is 6, XI is 11, and LX is 60.
Cardinals count. Learn unus, duo, tres, quattuor, quinque, sex, septem, octo, novem, decem, undecim, duodecim, tredecim, quattuordecim, quindecim, sedecim, septendecim, duodeviginti, undeviginti, viginti, then centum and mille. Ordinals put things in a line: primus, secundus, tertius, quartus, quintus, sextus, septimus, octavus, nonus, decimus. Duodeviginti means two from twenty, which is 18. Undeviginti is 19.
Examples
- XIV — 14 X and then IV: ten plus four.
- XL — 40 Ten before fifty subtracts.
- CM — 900 One hundred before one thousand subtracts.
- duodeviginti — 18 Two taken from twenty.
- decimus — tenth An ordinal, not the cardinal decem.
Latin in this lesson
- XIV — 14
- XL — 40
- C — 100
- M — 1000
- duodeviginti — 18
- decimus — tenth