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Roman Numerals. Write these notes in your spirals!. Roman Numerals. Are expressed by letters of the alphabet. I = 1 V = 5 X = 10 L = 50 C = 100 D = 500 M = 1000. I V alue X ylophones L ike C ows D o M ilk. Rules. A letter repeats its value as many times as it appears
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Roman Numerals Write these notes in your spirals!
Roman Numerals • Are expressed by letters of the alphabet. • I = 1 • V = 5 • X = 10 • L = 50 • C = 100 • D = 500 • M = 1000 • I • Value • Xylophones • Like • Cows • Do • Milk
Rules • A letter repeats its value as many times as it appears X = 10 XX= 20 XXX= 30 • BUT… • Values can only repeat 3 times • The “fives” (V, L, D) do NOT repeat
Rules • If one or more letters are placed after letters of greater value, add the values together. • VI = 6 (5 +1) • MC = 1100 (1000+100) • If a letter is placed before a letter of greater value, subtract that amount • IV = 4 (5-1) XL = 40 (50-10) • IX = 9 (10-1) XC = 90 (100-10) • CD = 400 (500-100) CM=900 (1000-100) THESE ARE THE ONLY “LEGAL” SUBTRACTION PAIRS!
Rules • Except for the “legal” subtraction pairs, Roman numerals descend in value from left to right. • MMDCCLXVI = 2766 (1000 + 1000 + 500 + 100 + 100 + 50 + 10 + 5 + 1) • MCMXCIX = 1999 [1000+(1000-100)+(100-10)+(10-1)]