## Commonly Used Number Systems

Why do we count in 10's? Obviously because we have 10 fingers. It is not though preordained that we should count in 10's.

The Yoruba people of West Africa have a number system based on counting in 20's.

Computers use binary code, counting in 2's - using the symbols 0 and 1.

<> Clocks use 60's and 24's - 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day.Angles use 60's and 360's - 60 arc seconds in an arc minute, 60 arc minutes in a degree, 360 degrees in a full turn.

Currencies mostly use the 100's - 100 pence to a pound etc.

Natural systems use lots of different bases. DNA can be written using 2's or 4's, there being 2^{2}-4 different bases which make up our genes.

There are subatomic particles called quarks, of which there are twelve, so could express quarks in base 12.

Hexadecimal or base 16 - using the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F is also commonly used in computer programming.

The Fahrenheit Scale Goes from 0 to 212, and there is a very special number, e=2.71828...., called the natural base, which occurs in many areas of maths, physics, biology and chemistry.