16
Six.
Using the digits of 1345678, there are 210 three digit numbers in which no digit is repeated.
Roman Numerals are just another way of writing numbers. The same as using the Chinese Numerals, or even our very own Arabic Numerals. Tally is another way of noting numbers. So anything could, in essence, precede or follow Roman Numerals, that could precede or follow Arabic Numerals or Tallies.
It could be: XXX-IX-MMXIII as in Roman numerals
772
4: 1999,9199,9919,9991
Romans used Roman numerals as their form of numbers. Romans needed Roman Numerals because they needed numbers to count, tell time, and do other things in life that involved numbers. Roman numerals were used because they could all be scribed using a flat chisel i.e X I V M.
There are 27 of them.
Greek numerals are a system of representing numbers using the letters of the Greek alphabet. They are also known as Milesian numerals, Alexandrian numerals, or alphabetic numerals. In modern Greece, they are still in use for ordinal numbers.
Number of 7 digit combinations out of the 10 one-digit numbers = 120.
24
You can select 9 numbers for the first digit, 8 numbers for the second digit, and 7numbers for the third digit; so 504 (e.g. 9*8*7) different three digit numbers can be written using the digits 1 through 9.