XXI in Roman numerals
2026-02-28 15:49 Diff
https://brightchamps.com/en-us/math/numbers/xxi-roman-numerals

Rule 1: Addition Method — In the addition method, you will combine different Roman numerals. When a smaller or the same number is placed after the larger number, we will simply add it -V(5) + I (1) = VI(6)

Rule 2: Repetition Method — In this method, a Roman numeral can only be used up to 3 times to get a larger value

I + I + I = III (3)

X + X + X = XXX (30)

But we can’t write XXXX for 40, it's XL (40)

Rule 3: Subtraction Method — In the above repetition method, we got to know that a symbol can’t be used more than 3 times, then how will we write 40? Here, we will use the subtraction method. If the smaller numeral is placed before the larger numeral, then you have to subtract the smaller numeral from the larger numeral. For example, if we take XL (40), the smaller numeral X (10) is subtracted from the larger numeral L (50). So, L (50) - X (10) = XL (40)


Rule 4: Limitation Rule — We can't repeat a number more than 3 times in Roman numerals. Instead of that, we will add and subtract. E.g. 4 is not to be written as IIII, instead write IV (subtraction method, i.e., 5-1=4). For ten (X), we can't use VV, as we have a specific letter for each value. For example, (V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000). As you can see, we have to use these symbols for specific values. Roman numeric system can be used easily by following these rules.