4:20 would be converted to 420 (four hundred twenty) so that would be CDXX. However to make it easier for one to read, I'd leave it as 2 separate numbers 4 and 20, or IV and XX aka IV:XX.
But normally, we don't use roman numerals for time in that way. A clock will only say the hour in roman numerals, but not the minutes.
C = 100 and D = 500 but 400 is written as CD (100 less than 500) X is 10 and 20 is simply XX (10 + 10) so 420 would be CDXX
Because of new rules introduced during the Middle Ages the way we write out Roman numerals today are different to the way the Romans actually did themselves and so they probably totalled these numerals in the following logical manner: CD-XL = LCDX LCDX+LX = CDXX CDXX+XC = DX DX+X = DXX = Total Converted into Hindu-Arabic numerals: 400-40 = 360 360+60 = 420 420+90 = 510 510+10 = 520 = Total Remember that in maths a minus minus is equal to a plus and therefore --X = X
CDXX
420 million can be written as 420,000,000 in digits.
If you mean 420, it is CDXX
420 in Roman Numerals
C = 100 and D = 500 but 400 is written as CD (100 less than 500) X is 10 and 20 is simply XX (10 + 10) so 420 would be CDXX
Because of new rules introduced during the Middle Ages the way we write out Roman numerals today are different to the way the Romans actually did themselves and so they probably totalled these numerals in the following logical manner: CD-XL = LCDX LCDX+LX = CDXX CDXX+XC = DX DX+X = DXX = Total Converted into Hindu-Arabic numerals: 400-40 = 360 360+60 = 420 420+90 = 510 510+10 = 520 = Total Remember that in maths a minus minus is equal to a plus and therefore --X = X
420 = 4.2 × 102
420% = 21/5
CDXX
420 million can be written as 420,000,000 in digits.
It is: 2*2*3*5*7 = 420
4.2
420/100
If you mean 420, it is CDXX
420 230