In schools and everyday life we are using Arabic
numerals, which have 10 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.
Ancient Romans used letters from Latin alphabet
to write numbers. There are seven basic
letters in Roman numerals: I, V, X, L, C, D, and M. Each of the letters have certain value and by
combining the letters together other numbers are created.
Roman Arabic
I 1
V 5
X 10
L 50
C 100
D 500
M 1,000
How do we create the numbers?
When you write the letters together you add the
values, except when the lower value proceeds the higher value. See examples
below:
Roman numeral
|
Equivalent to
|
Something to keep in mind
|
I
|
1
|
Only
I, X, C, and M
can
be subtracted
I
can only be subtracted from
V
or X
X
can only be subtracted from
L
or C
C
can only be subtracted from
D
or M
Never
subtract
V,
L, and D
|
II
|
1+1=2
|
III
|
1+1+1=3
|
IV
|
5-1=4
|
VI
|
5+1=6
|
VII
|
5+1+1=7
|
VIII
|
5+1+1+1=8
|
IX
|
10-1=9
|
XI
|
10+1=11
|
XX
|
10+10=20
|
XXX
|
10+10+10=30
|
Xl
|
50-10=40
|
LX
|
50+10=60
|
XC
|
100-10=90
|
CXX
|
100+10+10=120
|
cXL
|
100+50-10=140
|
CC
|
100+100=200
|
CD
|
500-100=400
|
DC
|
500+100=600
|
DCC
|
500+100+100=700
|
CM
|
1,000-100=900
|
MC
|
1,000+100=1,100
|
Now
the fun begins. Here are some cool examples:
DCCCLXXII
500
+ 100 + 100 + 100 + 50 +10 + 10 + 1 + 1 = 872
CMLV
C
before M, means 1,000 – 100 = 900,
L
= 50
V
= 5
900
+ 50 + 5 = 955
XCIX
X
before C means 100 – 10 = 90
I
before X means 10 – 1 = 9
90
+ 9 = 99
How
about going the other way:
994 = 900 + 90 + 4
900
= 1,000 – 100, lower value comes before higher: CM
90
= 100 – 10, lower before higher: XC
4
= 5 – 1, lower before higher: IV
CMXCIV
453 = 400 = 50 + 3
400
= 500 – 100, lower before higher: CD
50
= L
3
= III.
CDLIII
1,640 =
1,000 + 600 + 40
1,000
= M
600
= 500 + 100, means DC
40
= 50 – 10, lower before higher: XL
MDCXL
***
BIBLIOGRAPHY
Adler, David A., Fun With Roman Numerals, Holiday House, New York, 2008.
