You know that 2 + 2 = 4. But do you know
that ii + ii = iv?
The numbers that we normally use (1, 2, 3 etc) are
called "Arabic numerals". But we sometimes use another system for writing
numers - "Roman numerals". The Romans used letters of the alphabet to
represent numbers, and you will occasionally see this system used for page
numbers, clock faces, dates of movies etc.
There are 7 letters used
for Roman numerals:
I = 1 V = 5 X = 10 L = 50 C = 100
D = 500 M = 1000
In general, letters are placed in decreasing
order of value, eg XVI = 16. Letters can be repeated one or two times
to increase value, eg XX = 20, XXX = 30. Letters cannot be repeated three
times, so XXXX is not used for 40. In this case, XL = 40 (50 minus
10).
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