Father of decimal number system

Answer 1

The decimal (base 10) number system can be found in many of the world's oldest civilizations and records including the Egyptians (3000 BC), Minoans (1600 BC), Bronze Age Greeces (1900 BC), Indian Brahmi (300 BC), Hittites (1600 BC), and Chinese (1700 BC). As such, either the system was invented multiple times or the inventor lost in pre-history.

However, the first documented case of a decimal number system being invented is by Archimedes (287-212 BC) in his Sand Reckoner.