H Roman Numerals (1).ppt

Roman 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 !