# Roman Numberals

Roman Numerals, although very old, are still in use for distinct applications. For example, when a list is enumerated especially in old mathematics books, you can see the roman numerals there. Or they are still being use in clocks hanging on a wall. It’s certainly useful to know a few facts about the Roman numerals. Here are a few of the Roman numerals:

1. – I
2.  – II
3.  – III
4.  – IV
5.  – V
6.  – VI
7.  – VII
8.  – VIII
9.  – IX
10.  – X

After 10, number 11 would be for example would be XI or number 12 would be XII. Number 20 would be XX.

Here’s an overview of some of the larger Roman numerals:

I -> 1; V -> 5; X -> 10; L -> 50; C -> 100; D -> 500; M -> 1000.

There are a few rules regarding the Roman numerals. Knowing these rules, you’ll be able to read them if they get more complicated than the cases described above. You are usually not required to know the following rules but it does not hurt to know them:

Rule 1: If you repeat a numeral, its value will be added relative to the number of times you repeated it. Observe the following examples:

• To write the number 2 in Roman, you have to write the Roman 1 twice: II
• To write the number 20 in Roman, you have to write the Roman 10 Twice: XX

Rule 2: Although we said in Rule 1 that you can repeat “I” for example once to get to “II,” which is the number 2 in Roman, you are not supposed to repeat any numeral more than twice. In other words, no numeral may be written more than thrice in a row.

• For example, to write 30 in Roman, you repeat X twice, meaning that you write it once and repeat it twice so in total, you have three X’s. The number would be, “XXX.”But to write 40 in Roman you cannot write, “XXXX.” To do that, you’d have to write 50 and subtract 10 from it which would be, “XL.” We’ll talk about this subtraction in other rules.

One more part of Rule 2 is that the numerals V, L and D are not supposed to be repeated at all which stand for 5, 50 and 500 respectively.

Rule 3: This rule is somehow related to the “subtraction” we pointed to in the previous rule. To create the number 12 for example in Roman, you have to add 2 to 10. You do that by putting a 2 on the right hand side of 10. And you already know that a 2 in Roman is nothing but two 1’s. So the number becomes: XII. So from the example, you have hopefully understood that when you put a numeral of lower value to the right hand side of a numeral of higher value, the value of the numeral with the lower value will be added to the value of the numeral of the higher value.

Rule 4: This rule is the same thing as the previous rule but the other way around. To write the number 4 in Roman, you have to subtract 1 from 5. To do that, you write a Roman 1 on the “left” hand side of a Roman 5. That way the value of the numeral with a lower value on the left will be subtracted from the value of the numeral with a higher value on the right.

Also related to this subtraction rule, you never subtract the Roman 5, 50 and 500 (V, L and D respectively) from a numeral of greater value. Meaning that the three numeral will never be written on the left hand side of a numeral with a higher value than them.

Another related topic is the subtraction of Roman 1 which is “I.” The Roman 1 can be subtracted only from the Roman 5 and 10.

Another related topic is the subtraction of the Roman 10 which is “X.” The Roman 10 can be subtracted only from the Roman 50, 100 and 1000 (L, C and M respectively).

For your convenience, here’s a list of some Roman numbers:

• 1 -> I
• 2 -> II
• 3 -> III
• 4 -> IV
• 5 -> V
• 6 -> VI
• 7 -> VII
• 8 -> VIII
• 9 -> IX
• 10 -> X
• 20 -> XX
• 30 -> XXX
• 40 -> XL
• 50 -> L
• 60 -> LX
• 70 -> LXX
• 80 -> LXXX
• 90 -> XC
• 100 -> C

These articles are used by the author in a series of mathematics courses that will teach you mathematics from the sixth standard all the way up to 12th standard. The purpose of these courses are to help us understand mathematics so that you can use them professionally well. There is a road map that we have put together about the all the courses included, where to starts, etc. To know more about that and have access to those courses, please visit mathematics page on Great IT Courses. Thank you.

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