Question: why is 99 not ic in roman numerals?
Answer: 99 isn't IC because I (1) is 1/100th of C (100), not 1/10th. 49 isn't IL because I (1) is 1/50th of L (50), not 1/5th. 1400 isn't DCM because D (500) is less than 1000 (10 * 100 (C)).