1-4-5. Duodecimal
is another system of numerals in which the base is twelve. Compared to 10, 12
has more factors so it can be divided more easily, besides it can be counted by
fingers: excluding thumb, we have four fingers, each is divided into 3 parts or
consists of 3 finger bones; so we can count up to 12. We can use the thumb
moving over other fingers to count the amount.
We
need to define two symbols for ten and eleven. Either A and B, or T and E is
used to represent ten and eleven accordingly. Furthermore, a rotated 2 (ᘔ) and a reversed 3 (Ɛ) are proposed
by Sir Isaac Pitman as symbols for ten and eleven respectively.
Duodecimal
is also called dozenal system. That’s why we have a pack of dozen or half dozen
products especially drinks. Now we can see why 13 is considered as an unlucky
number. The 13th product, let’s say can of drink, can ruin the
divisibility of 12, moreover 13 is a prime number (it doesn’t have any factors
but 1 and itself) which will be discussed later. So imagine you wanted to share
12 cans of drink between six friends, and now you had 13 cans, what would you
do? Then the mythologies have amplified the unlucky power of 13.
That’s
also why the words eleven and twelve are different from teen numbers. They
stemmed from the Deutsche words elf and zwölf respectively.
In
order to compare different numeral systems, we need to know the fractions and
index form (that’s why I try to introduce them briefly), therefore, all
different bases will be discussed elaborately after the history of numerals
will have been discussed up to Hindu-Arabic numerals that we use these days. We
will try to develop all arithmetic operations based on different bases, then we
can compare their efficiency and drawbacks.