The number "five" in base five is represented by "10" That is:
1 × (five)1 + 0 × (five)0
The base in any positional representation is written as "10" (assuming that the usual symbols 0, 1, ... are used). Here is a number represented in base five: 421. It means:
421 = 4 × five2 + 2 × five1 + 1 × five0
Remember, the symbol "5" can not be used in the base five system. Actually, the above sum should be written as follows. (This looks just like base ten, but remember, here "10" is "five".)
421 = 4 × 102 + 2 × 101 + 1 × 100
To avoid confusion, sometimes the base being used is placed as a subscript: 4215 means that base 5 is being used. It is conventional to show the subscript in base 10.