Because of the changes made to the rules now governing the Roman numeral system introduced during the Middle Ages nowadays 1999, 19 and 199 when converted into Roman numerals are now configured as MCMXCIX, XIX and CXCIX respectively which restricts some sort of sensible arithmetical interaction amongst them.
Notwithstanding the aforementioned inasmuch that there exist historical evidence to suggest that the ancient Romans would have added together the given numbers in either of the following formats:-
A: IMM+IXX+ICC = MMCCXVII => (2000-1)+(20-1)+(200-1) = 2217.
B: MDCCCCLXXXXVIIII+XVIIII = MMXVIII => 1999+19 = 2018.
MMXVIII+CLXXXXVIIII = MMCCXVII => 2018+199 = 2217.
Note that the above calculations are fairly simple and straightforward to work out but for more complicated calculations the Romans would have used an abacus calculating device.
QED
See answer to question: ' How do you add together 1666 and 1999 in two different ways using Roman numerals'
Roman numerals are entirely inappropriate for doing such calculations. I believe the people in Roman times did such calculations on an abacus or something similar - which is basically similar to converting them to the Arabic numbers we use. If you really want to do it in Roman numerals - which is basically NOT a good idea - you would have to keep the thousands, hundreds, etc. separate, and handle carry (for addition) and borrowing (for subtraction).
When 9 is converted into Roman numerals it is IX which is an abridged version of VIIII and so the required calculations are as follows:-MDCCLXXVI+IX = MDCCLXXXV => 1776+(10-1) = 1785MDCCLXXVI+VIIII = MDCCLXXXV => 1776+9 = 1785MDCCLXXVI-IX = MDCCLXVII => 1776-(10-1) = 1767MDCCLXXVI-VIIII = MDCCLXVII => 1776-9 = 1767Note that in mathematics -(10-1) changes to 1-10QED
MIM + MMXIV = MMMXIII or MMCXCIX + MMXIII = MMMXIII There is only one way to write the solution (3013)
The modern way of expressing the equivalent of 444 into Roman numerals is now CDXLIV which does not lend itself quite easily for the purpose of calculations but there is historical evidence to suggest that the ancient Romans would have worked it out on an abacus counting device as CCCCXXXXIIII and then logically abridged it to IVLD in written format thus facilitating the speed and ease of the required calculations as follows:-MDCCLXXVI+IVLD = MMCCXX => 1776+(500-56) = 2220MDCCLXXVI+CCCCXXXXIIII = MMCCXX => 1776+444 = 2220MDCCLXXVI-IVLD = MCCCXXXII => 1776-(500-56) = 1332MDCCLXXVI-CCCCXXXXIIII = MCCCXXXII => 1776-444 = 1332Note that in mathematics -(500-56) changes to 56-500QED
See answer to question: ' How do you add together 1666 and 1999 in two different ways using Roman numerals'
Roman numerals are entirely inappropriate for doing such calculations. I believe the people in Roman times did such calculations on an abacus or something similar - which is basically similar to converting them to the Arabic numbers we use. If you really want to do it in Roman numerals - which is basically NOT a good idea - you would have to keep the thousands, hundreds, etc. separate, and handle carry (for addition) and borrowing (for subtraction).
When 9 is converted into Roman numerals it is IX which is an abridged version of VIIII and so the required calculations are as follows:-MDCCLXXVI+IX = MDCCLXXXV => 1776+(10-1) = 1785MDCCLXXVI+VIIII = MDCCLXXXV => 1776+9 = 1785MDCCLXXVI-IX = MDCCLXVII => 1776-(10-1) = 1767MDCCLXXVI-VIIII = MDCCLXVII => 1776-9 = 1767Note that in mathematics -(10-1) changes to 1-10QED
MIM + MMXIV = MMMXIII or MMCXCIX + MMXIII = MMMXIII There is only one way to write the solution (3013)
Doing arithmetic with Roman numerals is exasperating, and imho a pointless waste of time, except to demonstrate the obvious superiority of our "normal numbers," which use base-10 radix / positional notation that includes a zero digit as a placeholder. I'd venture to say science & technology -- commerce, too -- could never have developed in recent centuries if we still used Roman numerals for calculations. However, this web site explains some methods: http://turner.faculty.swau.edu/mathematics/materialslibrary/roman/
Since you ask how I would do it: I would forget about doing this in Roman; rather, I would convert everything to arabic numbers, which are much more appropriate for such calculations.
Under today's modern rules now governing the Roman numeral system the equivalent of 249 when converted into Roman numerals is now considered to be CCXLIX which does not lend itself quite easily to arithmetical operations but there exist credible evidence to suggest that the ancient Romans would have carried out the requested calculations as follows:-MDCCLXXVI+ICCL = MMXXV => 1776+(250-1) = 2025MDCCLXXVI+CCXXXXVIIII = MMXXV => 1776+249 = 2025MDCCLXXVI-ICCL = MDXXVII => 1776-(250-1) = 1527MDCCLXXVI-CCXXXXVIIII = MDXXVII => 1776-249 = 1527Note that in mathematics -(250-1) becomes -250+1 or as 1-250The above calculations were fairly simple and straight forward to work out but for more complicated calculations the Romans would make use of an abacus calculating device.QED
Numerals are used for mathematical calculations. Mathematical calculations are used in science. This is the way Roman numerals related to Roman science.
Latin numeracy is the same as Roman numerals and under the modern rules now governing the Roman numeral system the equivalent of 549 when converted into Roman numerals is now considered to be DXLIX but there exist historical evidence to suggest that the ancient Romans would have worked it out on an abacus counting device as DXXXXVIIII which can be abridged to IDL thus expediating the speed and ease of the required calculations as follows:-MDCCLXXVI+IDL = MMCCCXXV => 1776+(550-1) = 2325MDCCLXXVI+DXXXXVIIII = MMCCCXXV => 1776-449 = 2325MDCCLXXVI-IDL = MCCXXVII => 1776-(550-1) = 1227MDCCLXXVI-DXXXXVIIII = MCCXXVII => 1776-549 = 1227QED
The rules as we know them today now governing the Roman numerals system had nothing to do with the Romans because they were introduced during the Middle Ages and as result of these rules the equivalent of 999 converted into Roman numerals is now considered to be CMXCIX which hardly lends itself quite easily for the purpose of mathematical operations but there exist credible evidence to show that the ancient Romans would have worked out the requested calculations as in the following formats:-MDCCLXXVI+IM = MMDCCLXXV => 1776+(1000-1) = 2775MDCCLXXVI+DCCCCLXXXXVIIII = MMDCCLXXV => 1776+999 = 2775MDCCLXXVI-IM = DCCLXXVII => 1776-(1000-1) = 777MDCCLXXVI-DCCCCLXXXXVIIII = DCCLXXVII => 1776-999 = 777Note that in mathematics -(1000-1) becomes 1-1000 and that the above calculations were fairly simple and straightforward to work out but for more advanced calculations the Romans would have used an abacus calculating device.QED
In today's modern conversion of Roman numerals 49 and 19 are now considered to be XLIX and XIX respectively but the ancient Romans would have probably worked out the above as follows:- IL+IXX = LXVIII => (50-1)+(20-1) = 68 XXXXVIIII+XVIIII = LXVIII => 49+19 = 68 IL-IXX = XXX => (50-1)-(20-1) = 30 XXXXVIIII-XVIIII => 49-19 = 30 For more complicated calculations the Romans would use an abacus calculating device.
The modern way of expressing the equivalent of 444 into Roman numerals is now CDXLIV which does not lend itself quite easily for the purpose of calculations but there is historical evidence to suggest that the ancient Romans would have worked it out on an abacus counting device as CCCCXXXXIIII and then logically abridged it to IVLD in written format thus facilitating the speed and ease of the required calculations as follows:-MDCCLXXVI+IVLD = MMCCXX => 1776+(500-56) = 2220MDCCLXXVI+CCCCXXXXIIII = MMCCXX => 1776+444 = 2220MDCCLXXVI-IVLD = MCCCXXXII => 1776-(500-56) = 1332MDCCLXXVI-CCCCXXXXIIII = MCCCXXXII => 1776-444 = 1332Note that in mathematics -(500-56) changes to 56-500QED