Roman to Arabic numbers
The Wikipedia says that the Roman numerals are now written with letters of the Roman alphabet where as they were originally independent symbols. Arabic number use is the common practice but use of roman number is not inappropriate. Hence, it is nice to know how they are used. Very general rule is to remember the following syntax and combination of the same results to different numbers in Arabic or vice verse.
I=1
II=2
III=3
IV=4
V=5
VI=6
VII=7
VIII=8
IX=9
X=10
XL=40
L=50
XC=90
C=100
CD=400
D=500
CM=900
M=1000
From the above table it shows that the roman numbers has basic symbols like I, V, X, L, C, D, and M.
To remember in easy way, numbers can be categorise into its position like units, tenth, hundred, and thousands. In each category, a new symbol arises for one back combination of middle and last number. The back number is a 'position' unit less i.e., for units position, it is unit less; for tenth position, it is 10 less; for hundred it is 100 less. The main symbols are:
I-V-X for units position
X-L-C for tenth
C-D-M for hundred
M - - for thousand
Example, unit category:
1 or I is first unit. 5 (V) and 10 (X) are the middle and last numbers so a new symbols arises before 5 and 10. A unit less for middle (5-1=4) is represented by first unit and middle unit i.e., IV. Similarly, for last unit of this category (10-1=9), it is represented by first unit and last unit i.e., IX.
Tenth category:
Starting or first unit is 10 (X). Middle unit is 50 (L) and last unit is 100 (C). Hence, there should be new numbers for a unit less for middle (50-10=40) and last (100-10=90). A number before middle number (40) is represented by first unit (X) of the category and middle number i.e., XL and last number (90) as first unit (X) and last number (C) i.e., XC.
Hundred category
Starting or first unit is 100 (C). Middle unit is 500 (D) and last unit is 1000 (M). Hence, there should be new numbers for a unit less for middle (500-100=400) and last (1000-100=900). A number before middle number (400) is represented by first unit (C) of the category and middle number i.e., CD and last number (900) as first unit (C) and last number (M) i.e., CM.
Thousand category
Starting or first unit is 1000 (M). Middle unit is 5000 (V bar) and last unit is 10000 (X bar). Hence, there should be new numbers for a unit less for middle (5000-1000=4000) and last (10000-1000=9000). A number before middle number (4000) is represented by first unit (V bar) of the category and middle number i.e., MVbar and last number (9000) as first unit (X bar) and last number (V bar) i.e., Vbar Xbar.
In all the cases the forth numbers are the combination of normal symbols in a sequence from highest numbers to units like, thousands place are replaced with thousands category symbols, then hundreds, then tenth and units at the end. The highest symbol of each category available is use in each case.
Example: 66. It can be written as six times XXXXXXVI where six times X represents 60 and VI as six but 66 has to be written as 60+6 and for 60 which is under tenth category and neariest number is 50 having symbol. Hence, L is use for 50 now remaining 16 is represented as 10+6 where 10 has symbol X and 6 is nearest to units middle number (5) having symbol V plus one (I). Hence their combination, X and V and I gives LXVI for 66.
Another example, to represent, 99, it is tenth category unit so it can not be written as a unit less than hundred (100-1=99) or (IC). It has to be written as 90+9. 90 has a symbol XC and 9 has IX so 99 is XCIX. In similar manner, 4687, it is categorised as 4000+600+80+7. So it is MMMMDCLXXXVII.
To convert roman to Arabic or vice verse, please visit:
http://www.guernsey.net/~sgibbs/roman.html
I=1
II=2
III=3
IV=4
V=5
VI=6
VII=7
VIII=8
IX=9
X=10
XL=40
L=50
XC=90
C=100
CD=400
D=500
CM=900
M=1000
From the above table it shows that the roman numbers has basic symbols like I, V, X, L, C, D, and M.
To remember in easy way, numbers can be categorise into its position like units, tenth, hundred, and thousands. In each category, a new symbol arises for one back combination of middle and last number. The back number is a 'position' unit less i.e., for units position, it is unit less; for tenth position, it is 10 less; for hundred it is 100 less. The main symbols are:
I-V-X for units position
X-L-C for tenth
C-D-M for hundred
M - - for thousand
Example, unit category:
1 or I is first unit. 5 (V) and 10 (X) are the middle and last numbers so a new symbols arises before 5 and 10. A unit less for middle (5-1=4) is represented by first unit and middle unit i.e., IV. Similarly, for last unit of this category (10-1=9), it is represented by first unit and last unit i.e., IX.
Tenth category:
Starting or first unit is 10 (X). Middle unit is 50 (L) and last unit is 100 (C). Hence, there should be new numbers for a unit less for middle (50-10=40) and last (100-10=90). A number before middle number (40) is represented by first unit (X) of the category and middle number i.e., XL and last number (90) as first unit (X) and last number (C) i.e., XC.
Hundred category
Starting or first unit is 100 (C). Middle unit is 500 (D) and last unit is 1000 (M). Hence, there should be new numbers for a unit less for middle (500-100=400) and last (1000-100=900). A number before middle number (400) is represented by first unit (C) of the category and middle number i.e., CD and last number (900) as first unit (C) and last number (M) i.e., CM.
Thousand category
Starting or first unit is 1000 (M). Middle unit is 5000 (V bar) and last unit is 10000 (X bar). Hence, there should be new numbers for a unit less for middle (5000-1000=4000) and last (10000-1000=9000). A number before middle number (4000) is represented by first unit (V bar) of the category and middle number i.e., MVbar and last number (9000) as first unit (X bar) and last number (V bar) i.e., Vbar Xbar.
In all the cases the forth numbers are the combination of normal symbols in a sequence from highest numbers to units like, thousands place are replaced with thousands category symbols, then hundreds, then tenth and units at the end. The highest symbol of each category available is use in each case.
Example: 66. It can be written as six times XXXXXXVI where six times X represents 60 and VI as six but 66 has to be written as 60+6 and for 60 which is under tenth category and neariest number is 50 having symbol. Hence, L is use for 50 now remaining 16 is represented as 10+6 where 10 has symbol X and 6 is nearest to units middle number (5) having symbol V plus one (I). Hence their combination, X and V and I gives LXVI for 66.
Another example, to represent, 99, it is tenth category unit so it can not be written as a unit less than hundred (100-1=99) or (IC). It has to be written as 90+9. 90 has a symbol XC and 9 has IX so 99 is XCIX. In similar manner, 4687, it is categorised as 4000+600+80+7. So it is MMMMDCLXXXVII.
To convert roman to Arabic or vice verse, please visit:
http://www.guernsey.net/~sgibbs/roman.html
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