IX Roman Numerals

What is IX in Roman Numerals?

IX in Roman numerals equals the number 9.

This is because:

I = 1
X = 10

As can be seen on our main Roman numerals page under the heading “The Subtractive Principle”, because the smaller number (in this case I which equals 1), is written before the larger number (in this case X which equals 10), then the smaller number is taken away from the bigger number.

So even though it is written as IX, the whole equation works out as:

X (10) minus I (1) which equals 9.

If the I was written after the X, the two numbers would be added together, as the smaller number has come after the bigger one. So in this example, XI in Roman numerals would equate to X + I, or 10 + 1, which equals 11.

Math Questions Containing the Roman Numerals IX
Why not have a go at solving some of the math equations below which each contain the Roman number for 9, IX, in them somewhere?

1. What is V plus IX?

We already know from above that the Roman numerals IX = 9, so all we have to do to solve this question is add 9 to the number represented by V, which is 5.

So the answer is 5 + 9, which equals 14 (or XIV in Roman numerals). N.B. Notice that 14 is not written as XIIII, as the number 4 in Roman numerals is IV, which again uses the subtractive principle that we use for working out the number for IX.

2. What is XI – IX?

This palindrome equation would be slightly more difficult if we hadn’t already shown above what number XI translated as!

We saw earlier that XI is equal to the number 11 because it is X (10) plus I (1). So taking IX (9) from XI (11) gives us the answer of 2 (or II in Roman numerals).

3. What is IX multiplied by III?

A simple multiplication sum this one. IX (9) multiplied by III (3) equals 27 (or XXVII in Roman numerals).

4. What is IX multiplied by LIV?

A slightly trickier multiplication equation, but very similar to the one above once you know what LIV is in Roman numerals.

LIV is L (50) plus V (5) minus I (1)… remember the subtractive principle because I comes before V! So, LIV = 50 + 5 – 1 which equals 54.

Now that we know that LIV = 54, and we know that IX = 9, we simply multiply the two together to get the rather large number of 486. In Roman numerals, this is CDLXXXVI. Want to understand the whole sum? It’s:

D (500) – C (100) plus L (50) plus X (10) plus X (10) plus X (10) plus V (5) plus I (1).

Phew!

Sometimes when dealing with large Roman numeral numbers such as this, and especially when there is a subtraction needed, it can sometimes be easier for you to work it out if you split the equation into two or more parts.

In this example, it is better (particularly when you are first getting started learning how to read Roman numerals, to work out the first part of CD (500 minus 100) to get your starting number of 400, and then just add on the rest to it.

5. What is XLV divided by IX?

Another tricky one to finish with that again involved that subtractive principle to work out what XLV equates to.

As the smaller number, X (10), comes before the bigger number, L (50), we need to subtract X from L, so we subtract 10 from 50 which gives us 40. Then we just add on the V (5), to give a total of 45.

Dividing 45 by IX (9) gives us the answer of 5 (or V in Roman numerals).

Remember, if you’re finding it difficult to get your head around and understand Roman numerals, you are certainly not alone, and even people who have been reading and converting them for a long time still have to take a moment to make sure they have correctly translated it into modern numbers.

Feel free to use the Roman numeral converter tool on our main Roman numerals page, which can convert both Roman numerals into modern-day numbers, or type in a number to convert it into Roman numerals, as this can help in seeing the correct number so that you can work out how it is put together.

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