Under todays rules governing the Roman numeral system, which had nothing to do with the Romans themselves because they were introduced after the Dark Ages, 1999 is now officially considered to be MCMXCIX which is rather remarkable inasmuch that mathematical integration with other numerals is hardly possible.
But there is evidence to suggest that the Romans would have actually calculated the equivalent of 1999 on an abacus counting device as MDCCCCLXXXXVIIII and then probably abridged it to IMM (2000-1) in written format thus facilitating the speed and ease of addition as follows:-
IMM+DCLXVI = MMDCLXV (2000-1)+(666) = (2665)
Alternatively:-
MDCCCCLXXXXVIIII+DCLXVI = MMDCLXV (1999)+(666) = (2665)
Note that: 5*I=V, 2*V=X, 5*X=L, 2*L=C, 5*C=D and 2*D=M
Roman numerals: M=1000, D=500, C=100, L=50, X=10, V=5 and I=1
QED
I expect a Roman would notice that 1999 is only I less than MM, so he would used MM plus the others, take-away one I. Similarly for the others. So you have MM+XX+L less III = MMLXVII. In two different ways: take off the III before adding LXX or take it off afterwards instead.
MMXIIII as the alternate (on clocks for example) version of number 4 is IIII
Today we write out 1999 in Roman numerals as MCMXCIX because of changes made to the rules governing the Roman numeral system during the Middle Ages and to add these numerals to MDCCLXXVI is almost impossible. But the Romans themselves would have calculated 1999 on an abacus counting device as MDCCCCLXXXXVIIII and probably simplified them to IMM by placing I to both sides of the numerals. So: MDCCLXXVI + (-I+MM) = MMMDCCLXXV (3775)
Officially in accordance with todays guidelines governing the Roman numeral system 1999 when converted into Roman numerals is MCMXCIX which makes addition with other numerals an almost impossible task.But during the classical Roman period the equivalent of 1999 would have been calculated on an abacus counting device as MDCCCCLXXXXVIIII which then can be abridged to IMM (2000-1) in written form thus facilatating the speed and ease of addition as follows:-MDCCLXXVI+IMM = MMMDCCLXXV (1776)+(2000-1) = (3775)Alternatively:-MDCCLXXVI+MDCCCCLXXXXVIIII = MMMDCCLXXV (1776)+(1999) = (3775)Note that: 5*I=V, 2*V=X, 5*X=L, 2*L=C, 5*C=D and 2*D=MRoman numerals: M=1000, D=500, C=100, L=50, X=10, V=5 and I=1QED
4.5 = SV (-0.5+5=4.5) Because: 4.5 = IIIIS which can be simplified to SV And: II*IIIIS = VIIII which can be simplified to IX Roman Numerals: M=1000, D=500, C=100, L=50, X=10, V=5, I=1 and S=1/2
They are both the same because in todays modern notation of Roman numerals the equivalent of 1999 is MCMXCIX which means 1000+900+90+9 = 1999 But the ancient Romans would have probably gone for the simpler version of IMM which means 2000-1 = 1999
Today we would convert 998,001 and 1,999 into Roman numerals as (CMXCVIII)I and MCMXCIX respectively which are incompatible with each other for the purpose of addition.But notwithstanding todays configuration of these numerals inasmuch that there is evidence to suggest that the ancient Romans would have calculated the equivalent of these numbers in either of the following formats:-(IIM)I+IMM = (M) => [1,000,000-2,000]+1+[2,000-1] = 1,000,000Alternatively:-(DCCCCLXXXXVIII)I+MDCCCCLXXXXVIIII = (M) => 998,001+1,999 = 1,000,000Remember: 5*I=V, 2*V=X, 5*X=L, 2*L=C, 5*C=D and 2*D=MRoman numerals: M=1000, D=500, C=100, L=50, X+10, V=5 and I=1Note that numerals within brackets indicate multiplication by a thousand and that the practice of placing a bar above a numeral to indicate multiplication by a thousand was introduced during the Middle Ages along with other rules and regulations now governing todays Roman numeral system.QED
In a poem
Your calculations can be more precise, but the final result should be rounded, to avoid giving the impression that it is more exact than is justified by the measurements.
Math teachers are expected to make accurate calculations.
XIX is the correct roman numeral for 19.Another Answer:-Nowadays it is XIX but in ancient Rome it was IXX because its Latin word is undeviginti meaning one from twenty and there is no Latin word for the equivalent of XIX
The rules governing the Roman numeral system were set in the Middle Ages and as a result today we would write out 999 in Roman numerals as CMXCIX which makes it almost impossible for them to intermingle with other numerals.But the Romans in the past would have probably calculated the equivalent of 999 on an abacus counting device as DCCCCLXXXXVIIII and changed it to IM in written form which makes addition straightforward as follows:-DCLXVI+IM = MDCLXV => (666)+(1000-1) = (1665)Alternatively:-DCLXVI+DCCCCLXXXXVIIII = MDCLXV +> (666)+(999) = (1665)Note that: 5*I=V, 2*V=X, 5*X=L, 2*L=C, 5*C=D and 2*D=MRoman numerals: M=1000, D=500, C=100, L=50, X=10, V=5 and I=1QED