【為什麼"一打" = 12?】

Dozen is another word for the number twelve. The dozen may be one of the earliest primitive groupings, perhaps because there are approximately a dozen cycles of the moon or months in a cycle of the sun or year. The dozen is convenient because its multiples and divisors are convenient: 12 = 2 × 2 × 3 = 3 × 4 = 2 × 6, 60 = 12 × 5, 360 = 12 × 30. The use of twelve as a base number, known as the duodecimal system (also as dozenal), probably originated in Mesopotamia (see also sexagesimal).

12的因數較多，以12件來包裝貨物較方便。
1排的包裝：1X12
2排的包裝：2X6
3排的包裝：3X4
（4排的包裝：4X3）

較我們常用的“10”更方便
1X10
2X5
5X2

中國古時有時係用12進制
正如時辰(子.酉...)生肖