M=1000
D=500
C=100
L=50
X=10
V=5
I=1
CDXLVII+XVI/IV
To change CDXLVII from Roman to Arabic numerals,
first we group it as follows:
Going left to right,
C to D is an increase
D to X is a decrease
X to L is an increase
L to V is a decrease
V to I is a decrease
I to I is the same
Group the pairs which show an increase or "the same" going
left to right.
(CD)(XL)V(II)
The C BEFORE the D means to SUBTRACT 100 from 500 and get 400.
The X BEFORE the L means to SUBTRACT 10 from 50 and get 40.
The V just means 5. (Ungrouped letters just get their value)
The I and the I are the same, so we ADD 1+1 and get 2.
So CDXLVII = 400+40+5+2 = 447
To figure out XVI
X to V is a decrease
V to I is a decrease
So there are no increases to group, so we just add their
individual values:
XVI = 10+5+1 = 16
To figure out IV
I to V is an increase, so we group them as
(IV)
Since the I is before the V, we subtract 1 from 5 and get 4.
CDXLVII+XVI/IV
447+16/4
447+4 = 451
Edwin
(