Question

Write the roman numeral of the following – 900.

Answer 1

Hint: We must use the knowledge of the basic representation of various Roman numerals and the rules that must be followed to convert a Hindu-Arabic numeral to a Roman numeral. So, we can represent the given number 900 as the difference of two numbers whose basic Roman numerals are known. We must use the fact that M represents 1000 and C represents 100. Now, we can easily represent 900 as 1000 – 100.

Complete step by step answer:
Let us first understand what are roman numerals. There are two ways of representing numbers. One is the Hindu-Arabic numerals and the other is the Roman numerals. The representation of numbers using digits like 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 come under the Hindu-Arabic numerals. The representation of numbers using capital letters like I, V, X, L, M… comes under the Roman numerals.
Now, let us write down the various letters and what they indicate as below,

Roman Numerals	Numbers
I	1
V	5
X	10
L	50
C	100
D	500
M	1000

Here we can see that we have notations for 1 and 5. So, if we have to represent numbers like 2, 3, 4, we need to follow some rules. Some of the rules are:
1. The basic digits are represented by letters I, V, X, L, C, D and M.
2. The order of placing the numeral is such that the largest value is placed first.
3. We have to add the values of the numbers if a higher numeral is placed before a smaller numeral.
4. We have to subtract the lower numeral from the higher numeral if a higher numeral is placed after a smaller numeral.
5. One numeral can be repeated maximum of three times in a row.
6. Numerals V, L, and D appear only once and not more than once consecutively.
7. We cannot subtract a numeral from another numeral which is more than 10 times greater.
We have got a fair idea of the rules and representations. So, now let us try representing the number 900 as a Roman numeral.
We can represent 900 as 900 = 1000 – 100
The numerals for 1000 and 100 are known. They are M and C respectively. We require 900, so we have to deduct 100 from 1000 as per the rules. So, we must place the higher numeral after the lower numeral. So, we can write it as CM.
Hence, we can represent 900 as CM.

Note:
 The rules and all the basic numerals must be learned well before appearing for exams and answering questions of this type. This will help in getting the answer right. Here, we can note that the number 900 could be expressed as CM since the difference between the numerals C and M was exactly 10o, which 10 times of lower numeral. So, we could use the notations. But, if we were to convert 800, then the difference would have been 200, which is greater than 10 times. So, we would represent 800 as 500 + 100 + 100 + 100 = DCCC and not as 1000 – 100 – 100 = CCM.