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Roman Numerals (page 2 of 2) Continuing our counting, we have: XV = 10 + 5 = 15 Eventually, we'll get to larger numbers. If we continue using these rules, we can create expressions for whatever values we are given. Let's work some examples.
The biggest numeral smaller than 400 is the C for 100. But I can't do CCCC for the 400, because that's four of the same character in a row. Instead, I have to subtract 100 from 500: CD = 500 – 100 = 400. Copyright © Elizabeth Stapel 2013 All Rights Reserved The 50 is easy: that's just L. For the 3, I use three Is. Then my answer is: 453 = CDLIII
Note: This number is one that you might actually see expressed in Roman numerals because, for some reason, the production dates on movies are written in Roman numerals. The smallest numbercharacter less than 1900 is 1000: M. After taking care of the thousand, I've got the 900 part of the number. I could start with a D for 500 and then add four Cs for the 400, but I can't use four of the same character in a row. So I'll instead use subtraction to get the 900: one hundred from one thousand is nine hundred, so 900 = CM. The next part of the number is the 80; the largest numbercharacter smaller than this is L for 50. Then I'll add three Xs for the three tens: 80 = LXXX. I'm left then with the nine, which is written as "one from ten": IX. Putting it all together, I get: 1000 + (1000 – 100) + 50 + 30 + (10 – 1) = 1989 = MCMLXXXIX
At the start of this Roman number is M which is 1000. Then comes D which is 500, followed by three Cs which is 300, for a total of 800. Then I've got an X which is 10, but that's followed by another C, which means that the 10 is subracted from 100. In other words, the XC is a 90. After that comes VII which I recognize as being 5 + 1 + 1 = 7. The year is 1,000 + 500 + 300 + 90 + 7 = 1897
Interesting fact: Though our letters are Latin (that is, Roman), our numerals came to us through MiddleAges North Africans; that is, from Arab scholars. So "Arabic numerals" is just a fancy way of saying "the digits we normally use". You might think that I could just subtract one from five hundred: ID. But that's too much of a subtraction. In general, I can only subtract 1, 10, or 100 from the next one or two numerals bigger. That is, I can subtract 1 from 10 or 50, but nothing bigger; I can subtract 10 from 50 or 100; and I can subtract 100 from 500 or 1,000, but that's it. (Why? "Because".) So I have to add up to 499, rather than subtracting down from 500. The biggest numeral smaller than 499 is 100, but I can't add up to 100 by using four Cs; instead, I have to subtract 100 from 500. This leaves me with the 99. While I can't subtract a 1 from a 100 to get 99, I can subtract a 10 from 100 to get 90. Then I can subtract a 1 from a 10 to get 9. Putting it all together, I get: (500 – 100) + (100 – 10) + (10 – 1) = 400 + 90 + 9 = CDXCIX To summarize:
Always build numbers starting with the biggestvalued character that you can squeeze into the number they've given you, and use subtractive forms wherever you can. << Previous Top  1  2  Return to Index



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