 # Roman Numerals Past and Present Romans used a number system for commerce Romans used a number system for commerce Initially began by using tally marks.

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Roman Numerals

Past and Present Romans used a number system for commerce Romans used a number system for commerce Initially began by using tally marks Initially began by using tally marks Still used today in different ways Still used today in different ways

Roman vs. Arabic Numerals Arabic numbers are Used but not in Arabic numbers are Used but not in standard for today everyday math standard for today everyday math foundation is foundation is 1,2,3,4,5,6,7,8,9,0 the base ten I, V, X, L, C, D, M 1,2,3,4,5,6,7,8,9,0 the base ten I, V, X, L, C, D, M system system numbers can be no symbol for zero numbers can be no symbol for zero repeated more repeated more than 3 times than 3 times

The Basics of Roman Numerals I = one (1) V = five (5) X = ten (10) L = fifty (50) C = one hundred (100) D = five hundred (500) M = one thousand (1,000)

Rules for Writing Roman Numerals 1) Letters should be arranged from largest to smallest -1510 is written MDX, largest to smallest 2) Only powers of ten can be repeated. 3) Letters can not be repeated more than 3 times in a row except for I -100 is written LL, not XXXXXXXXXX

Rules continued……. 4) Numbers can be written using subtraction with the first letter being smaller than the letter that follows (the smaller number is written to the left of the larger number) Example: -Nine (9) is written as IX (1 taken away from 10 or 1-10/10-1) -nine hundred and ninety is written as (10 taken away from 1,000) + (100-10) (10 taken away from 1,000) + (100-10) XM + XC = XMXC XM + XC = XMXC -249 is written as 100+100+ (50-10) + (10-1) = C C XL IX CCXLIX - How would you write 40, 92, 499?

When in Rome, do as the Romans do!! Abide by the customs of a society when one is a visitor.

Practice Number Conversions I = one (1) V = five (5) X = ten (10) L = fifty (50) C = one hundred (100) D = five hundred (500) M = one thousand (1,000) Practice 515 = ? 1005 = ? 32 = ? *993 = ? *19 = ?

Answers 515 = DXV 1005 = MV 32 = XXXII *993 = (1000-10) + (100-10) + 3 XM XC III = XMXCIII XM XC III = XMXCIII *19 = 10 + (10-1) X IX = XIX X IX = XIX

Adding the Roman Way Add 23 + 58 = show all your work using Roman Numerals Standard Number Roman Numeral 1I 5V 10X 50L 100C 500D 1000M

Adding the Roman Way How did they do that? Step 1. 23 + 58 Sept 2. XXIII + LVIII Sept 3. XXIIILVII Sept 4. LXXVIIIIII Sept 5. LXXVVI Sept 6. LXXXI Sept 7. 23 + 58 = LXXXI

Adding the Roman Way 77+ 32 = 345+60 = CCLVI + LXXXII = **LVI + XIX =

Answer 77+ 32 = CIX CCLVI + LXXXII = CCCXXXVIII LVI + XIX = LXXV

Congratulations!! Independent Practice Time

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