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Posted in: by jean-michel on January 22, 2006
Place-Value and Integer Base Notation
Positional notation is so intuitive that we grasp a fairly complex arithmetic equation with just a glance. We immediately understand 195.02 without having to add 5 to 90 to 100, and finally include the fraction 2/100. Positional sexagesimal is just as intuitive, with a little practice.
As you have probably guessed, “positional notation” means the position of each digit relative to the radix marker determines the magnitude of its value. The first place to the left of the radix marker represents the digit times the numerical base taken to the zeroth power (N0 always equals one), the second the digit times the numerical base to the first power, the third the digit times the numerical base squared, and so on. Similarly, the first position to the right of the decimal represents the digit times the numerical base taken to the negative one power, the second position the digit times the numerical base taken to the negative two power, and so on. The results are all added together, giving us the total value of the number. This is true of base 10, base 60, or any other numerical base you care to use.
Stated most generally, any number D can be represented in any base N (N>0) by a series of digits d as follows:
D = djNj + dj-1Nj-1 + … + d1N1+d0N0 . d-1N-1 + d-2N-2 + … + d-kN-k
Which, in standard positional notation, is written:
D = (djdj-1 … d1d0.d-1d-2 …)N,
where all digits d satisfy the constraint 0≤di<N.
Take, for example, the decimal (base 10) number “103.95”:
1 x 102 + 0 x 101 + 3 x 100 + 9 x 10-1 + 5 x 10-2 = 100 + 0 + 3 + 9/10 + 5/100
Which of course, gives us one hundred three and ninety-five hundredths, written in the familiar form of “103.95” in positional base 10.
Similarly, in sexagesimal, each position to the left of the radix marker represents increasing powers of 60, while those to the right of the radix marker represent increasing negative powers of 60. Consider:
Each symbol represents a number between zero and fifty nine. Just like in decimal notation, the position of the symbol defines the magnitude of its value. In the number above, m represents “48”, 0 is the same as “0” in decimal, 1 is “1”, “.” is the sexagesimal (radix) marker, F is “15”, and d is “39”.
Sexagesimal positional notation yields:
m x 602 + 0 x 601 + 1 x 600 + F x 60-1 + d x 60-2,
or, using numerals we are more familiar with:
48 x 602 + 0 x 601 + 1 x 600 + 15 x 60-1 + 39 x 60-2, which gives us:
172,800 + 0 + 1 + 15/60 + 39/3600 = 3648 939/3600, or the decimal value:
172,801.2608333… (3 recurring).
Notice how a three digit numeral in base 60 can represent a six digit base 10 number? The difference between decimal and sexagesimal notation grows dramatically with each digit.
© 2007, 2012 Jean-Michel Smith. All rights reserved.