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  • Stephen Knight

Learning Roman Numerals

Updated: May 20

Roman numerals are something that we all touch upon at some point in our school education. Often the "touch" though is light and relatively superficial. If however you want to delve a little deeper into what Roman numerals are and how to use them then dive on below!


If you feel that you don't know much about Roman numerals then why not check out the video below. In this video Stephen from Classroom Adventures looks at what the different Roman numerals are, what they mean and how to use them.



Putting it into Practice!


Now that you know a little bit more about Roman numerals it's time to put it into to practice. If you still look at Roman numerals and go all foggy trying to interpret them then don't worry, the more that you use them, the more familiar they will become and the more they will start to make sense.


Some people look down on Roman numerals as somewhat inferior to our modern, Arabic based, numerical system, and while solving mathematical equations has been attested to be a whole lot easier and faster than the Roman system, it does not mean that the Roman system is bad or rubbish. A day trip to Rome, or some of the other cities of the Roman empire will testify to the mathematical and engineering prowess of this long ago civilisation.


Just start by picking random numbers as they come to you and try to write them in Roman numerals. Here are some ideas:

  • The year of your birth

  • How much pocket money you have?

  • What size shoes do you wear?

  • How many children are in your year group?

  • What about in the whole school?


Okay, okay, here are some numbers that you can practice on as well:

  1. 48

  2. 15

  3. 72

  4. 486

  5. 1,294

  6. 58,487


And here are some Roman numerals for you to decipher. Break them up into chunks if you need to i.e. take MMMCDVIII and space out the sections like so: MMM CD VIII to show you the answer of 3,408:

  1. MCCXXXIV

  2. LVII

  3. DCLXVI

  4. MMLXXXVIII

  5. XIIII

  6. CMXCIX



Subtractive numerals? Really?


Actually the Romans used both subtractive and accumulative numbers so don't be afraid to use either. Subtractive numbers can make the overall number smaller to write (and read), but writing IIII instead of IV or DCCCC instead of CM is a totally legitimate thing to do. If you do write in subtractive just remember:

  1. you can only use the main place values, I (1), X (10) & C (100), to subtract from the larger number.

  2. you can only subtract up to the next place value i.e. (I from V or X), (X from L or C) and (C from D or M).

  3. you can only use one of them (so you can't write XXC instead of LXXX for 80, sorry)!



So where did it all start?


The Romans inherited their numerical system from the Etruscans (a much older powerful kingdom to the north of the Italian peninsula). The Etruscans started out with a simple tally of lines like so: IIII. Now it doesn't take long to realise that many lines without distinction are pretty hard to read like IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII (that's 44 by the way), so the Etruscans tilted every 9th line like this \ and every 10th line like this / (only they crossed them over to make this: X). So now 44 would look like this IIIIIIIIXIIIIIIIIXIIIIIIIIXIIIIIIIIXIIII (a lot easier to make out).


So pretty soon "I" came to simply value 1 and the 9th and 10th lines ("X") came to value 10. Now if i said to you "what is half of 10"? you would say "5". So what is half of X? Literally half of X is = 𐌡 (think of it being chopped in half horizontally) so 𐌡 came to represent 5 as it was half of X, or 10! Only by the time that Roman numerals became what we know today 𐌡 had got turned upside down to make V.



Feeling Brave?

If you are finding this super easy peasy then perhaps you might like to have a try at using the Latin names for the numbers here!

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