Maths
23/09/20
LO: To read Roman numerals to 1000
The Ancient Romans used letters to stand for numbers. Roman numerals were used in Europe until they were replaced by the Arabic numbers we use today. However, Roman numerals are still used for some things, such as the names of Kings and Queens or on some clock faces.
| Letter | Values |
|
I
V
X
L
C
D
M |
1
5
10
50
100
500
1000
|
Rules for forming numbers:
1 . Repeated numbers are added. V, L and D are never repeated.
Only repeat a number three times.
E.g. CCC= 100 + 100 + 100 = 300
2. Larger value first means add.
E.G. CXXVI = 100 + 10 + 10 + 5 + 1 = 126
3. Smaller values first means subtract
E.G. CMXC = 1000 - 100 + 100 - 10 = 990
Only subtract one number from another
80 is LXXX not XXC (50 + 30 not 100 -20)
Only subtract I, X and C, not V, L or D
450 is CDL not LD ( 400 + 50 not 500 - 50)
Only subtract the nearest value out of I, X and C
490 is CDXC not XD (400 + 90 not 500 -10)