A pre-Super Bowl refresher on Roman numerals

With Super Bowl XLVI approaching, a primer on Roman numerals:

I equals 1

V equals 5

X equals 10

L equals 50

C equals 100

D equals 500

M equals 1,000

Roman numerals are usually arranged in descending value and added up from left to right. But when a smaller number is placed before a larger one, the smaller value is subtracted from the larger one to the right.

For example: IV is 4, XL is 40 and CM equals 900. So MCMXLIV is 1944.

There are certain restrictions when subtracting. For example, 45 is written as XLV, not VL. And 49 is XLIX, not IL.

Source: Gerard Michon of -http://www.numericana.com