4.2 Outline

A. Hindu-Arabic numerals
     1. decimal numeration system
     2. algorists vs. abacists
B. Decimal system -grouping by tens
C. Expanded notation     
     1. meaning of a number
     2. decimal point

4.2 Essential Ideas  

The Hindu-Arabic or decimal numeration system is the one we use everyday. Its properties include:
1. It uses ten symbols, called digits.
2. Larger numbers are expressed in terms of powers of 10.
3. It is positional.

The essential idea of this section is expanded notation.