What are the roman numerals for 40 and why?

Answer 1

Forty written in roman numerals is XL.

Roman numerals are based, primarily, on a series of additions. I=1, V=5, X=10, L=50, C=100, D=500, M=1000. In present day, no more that three of the same numerals are written consecutively. i.e. The number three is written as III (I+I+I), the number 32 is written as XXXII (X+X+X+I+I).

Subtractive rules apply in order to achieve the number 4, which is thought of as one less than five or IV. The same applies to the number 9, which is thought of as one less than ten or IX. The number 40 is thought of as ten less than fifty.

When converting a number into roman numerals, write it from left to right beginning with the highest number and working across. (It is easier to think of the number broken down as ones, tens, hundreds, and thousands.) For example, consider the number 2317 as 2000+300+10+7 which is written as MMCCCXVII.

For numbers that include a 4 or a 9, subtractive rules apply, so writing 1952 would be considered as 1000+(100 less than 1000)+50+2 which is written MCMLII. The number 99 must be considered as 90+9 (ten less than 100+one less than ten) which is written as XCIX. It is tempting to think of 99 as one less than one hundred and write it as IC, but it is incorrect thinking. When you remember to consider a number broken down as ones, tens, hundreds and thousands, you will see that writing 99 as IC shows that the number was considered as ones and hundreds, omitting the tens.)

Answer 2

The Roman numeral for 40 is "XL." The reason is that the Romans represented 10 with the letter "X," and they subtracted it from 50, represented by the letter "L," to represent 40. By subtracting 10 from 50, they created the numeral "XL" for 40.