This document provides information about Roman numerals. It discusses the two main types of numbers, Arabic and Roman. It explains the history and development of Roman numerals, how they represented quantities and followed rules like not combining more than three of the same letter. The document outlines the basic Roman numerals and values (I, V, X, L, C, D, M), and rules for writing numbers like not exceeding three repeated letters and using larger values first. It provides subtraction rules and examples of writing different numbers in Roman numerals. Finally, it includes practice problems for writing numbers in Roman and Arabic numerals.

1. Roman Numerals
Medical Math in Health/Science Care

2. Two Types of numbers
 Arabic numbers
 The numbers we normally use
 1,2,3,4,,,,,,,,
 Roman Numbers
 Invented by the romans and still used today
 I, V, X, L, C, D, M

3. Hx of Roman numerals
 Romans strictly represented units as
separate items in their numbers.
 the numerals represented numbers as they
were depicted on an abacus - a calculating
machine using pebbles or beads which were
arranged from right to left in columns of
units, tens, hundreds, thousands etc.

4. Continued……
 That means that 99 could be represented as
XCIX - 90+9 but never as IC.
 XC = 10 subtracted from 100 = 90
 IX = 1 subtracted from 10 = 9
 90 + 9 = 99
 999 cannot be IM
 IM is not legal
 999 = CMXCIX
 CM = 100 from 1000=900, XC = 10 subtracted from
100 = 90 and IX = 1 subtracted from 10 = 9
 Therefore 900 + 90 + 9 = 999

5. Roman Numerals
You must Learn
 I = 1
 V = 5
 X = 10
 L =50
 C =100
 D = 500
 M = 1000

6. Roman Numeral Rules
 You can’t add more than 3 of the same letters at
one time.
– Ex: 4 is IV not IIII
 use the biggest numeral possible at each stage
– Ex: 15 XV not VVV or XIIIII.
 A smaller value letter to the left of a larger value
one is subtracted
– Ex: 34 is XXXIV not XXXIIII

7. Three Subtraction Rules
 Only I, X. and C can be subtracted
 Only one smaller number can be placed to
the left Ex: 9 = IX
 The subtracted number must be no less
than a tenth of the value of the number it is
subtracted from.
– I can only be subtracted from V & X
– X can only be subtracted from L & C
– C can only be subtracted from D & M

8. Three Subtraction Rules
 These rules only became official in the
Middle Ages. Even today, not everybody
follows them.
 Made to ensure compliance, set standards
and provide guidance.
 Made to be broken, some common
examples of broken rules are on clocks,
monuments and tombs.

9. Forming Numerals
 Numbers are formed by stringing the letters
together to add up to the number required.
 Examples
– II = 2 (1+1=2)
– XXX = 30 (10+10+10 = 30)
– XII = 12 (10+1+1= 12)
– CXXIII = 123 (100+10+10+1+1+1=123)

10. Examples of the official rules
for subtracting letters:
1. Subtract only powers of ten, such as I, X,
or C. Writing VL for 45 is not allowed: write
XLV instead.
2. Subtract only a single letter from a single
numeral. Write VIII for 8, not IIX; 19 is XIX,
not IXX.
3. Don't subtract a letter from another letter
more than ten times greater. This means
that you can only subtract I from V or X,
and X from L or C, so MIM is illegal.

11. Time to test your knowledge
Write the Roman Numeral
 1
 5
 10
 50
 100
 500
 1000

12. Write the Roman Numeral
 19
 724
 2008
 29
 3916
 200
 1549
 33
 64
 113

13. Write the Arabic #
 CCXXIV
 LXXXII
 DCCLXXV
 MCDXII
 MMMDDCDII
 MMIX
 CXXXVIII
 DXLIX
 CMLXIII
 XIV

14. Homework
 Create 10 roman numerals.
– Each number must contain a minimum of 2
Roman numerals
– Remember to follow your rules
– You need to understand this, so please take it
serious. Be able to explain your numbers to me.
– This counts as a grade.
Good Luck !