Express a given integral number in any scale (radix)

Several scales (radix) have been used by mathematicians. Binary (2), Ternary (3), Quaternary (4), Quinary (5), Senary (6), Septenary (7), Octenary(8), Nonary (9), Denary (10/Decimal), Undenary(11), Duodenary (12) and of course, hexadecimal (16). Note that in any scale the base radix is “10”. Thus, “10” stands for 2 in “binary”, “ten” in “decimal”, 8 for “octal” radix respectively, etc.

Let the digits used in a proposed scale(radix r) be a_{0}, a_{1}, a_{2}, \ldots, a_{n} . Let us express an integer in this scale. Let a_{0} be unit’s digits. Analagous to the place value system (in decimal):

N=a_{0} + a_{1} \times r^{1} + a_{2} \times r^{2} + \ldots + a_{n} \times r^{n}

Now, let us say we want to express this number N in terms of these digits a_{i}s.

Dividing N by r, we get the unit’s digit a_{0} as the remainder; and the quotient is:

a_{1} + a_{2} \times r^{1} + a_{3} \times r^{2} + \ldots + a_{n} \times r^{n-1}.

Dividing the above quotient by r, we get a_{1} as the remainder and the quotient as:

a_{2} \times r^{1} + a_{3} \times r^{2} + a_{4} \times r^{3} + \ldots + a_{n} \times r^{n-2}, and so on.

Example: Express the denary number 5213 in the scale of seven.

Solution: (5213)_{10} \div 7 gives 5 as remainder and (744)_{10} as quotient.

(744)_{10} \div 7 gives 2 as remainder and (106)_{10} as remainder.

Continuing this way, we are able to express:

(5213)_{10} = 2 \times 7^{4} + 1 \times 7^{3} + 1 \times 7^{2} + 2 \times 7 +5. That is (21125)_{7}. You can check the equivalence by converting both to decimal values.


Nalin Pithwa.

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