Roman numerals

Roman numerals--the letters you may see at the bottom of a movie screen, or as part of the publication information of an old book, or on an old-fashioned clock face, are easy to read once you learn them. Older children who can do a bit of math usually enjoy learning about them.
I  is one--1
V is five--5
X is ten--10
L is fifty--50
C is one hundred--100
D is five hundred--500
M is one thousand--1,000
The tricky (or fun)  part is how they are put together. Up to three (3) of a kind can be put together, and "added" to express a number. When four (4) are needed, the smaller number goes before the next, and is "subtracted".  For example--
I = 1
II = 2
III = 3
IV = 4
V = 5
VI = 6
VII = 7
VIII = 8
IX = 9
X = 10
XX = 20
XXX = 30
XL = 40
L = 50
LX = 60
LXX = 70
LXXX = 80
XC = 90
C = 100
CC = 200
CD = 400
D = 500
DC = 600
CM = 900
MM = 2000
MMXI = 2011
Numbers can get very long, with barely time to read them as screen credits roll by.

MCMLXXII = 1972
MCMXLVIII = 1948