Download Roman Numerals

Roman Numerals
Medical Math in Health/Science Care
Tina Marie Hunt, RN, BSN
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
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.
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
Roman Numerals
You must Learn
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I=1
V=5
X = 10
L =50
C =100
D = 500
M = 1000
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
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
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.
Forming Numerals
 Numbers are formed by stringing the letters
together to add up to the number required.
 Examples
– II = 2
– XXX = 30
– XII = 12
– CXXIII = 123
(1+1=2)
(10+10+10 = 30)
(10+1+1= 12)
(100+10+10+1+1+1=123)
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.
Time to test your knowledge
Write the Roman Numeral
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1
5
10
50
100
500
1000
Write the Roman Numeral
 19
 724
 2008
 29
 3916
 200
 1549
 33
 64
 113
Write the Arabic #
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CCXXIV
LXXXII
DCCLXXV
MCDXII
MMMDDCDII
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MMIX
CXXXVIII
DXLIX
CMLXIII
XIV
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 !