- Topics At a Glance
**Different Types of Numbers**- Natural Numbers
- Whole Numbers
- Integers and Negative Numbers
- Integers and Absolute Value
- Rational Numbers
- Irrational Numbers
- Real Numbers and Imaginary Numbers
- Different Ways to Represent Numbers
- Fractions
- Equivalent Fractions
- Mixed Numbers
- Reducing Fractions
- Comparing Fractions
- Least Common Denominator
- Addition and Subtraction of Fractions
- Multiplication of Fractions
- Equivalent Fractions and Multiplication by 1
- Multiplication by Clever Form of 1
- Multiplicative Inverses
- Division of Fractions
- Multiplication and Division with Mixed Numbers
- Decimals
- Converting Fractions into Decimals
- Converting Decimals into Fractions
- Comparing Decimals
- Adding and Subtracting Decimals
- Multiplication and Division by Powers of 10
- Multiplying Decimals
- Dividing Decimals
- Infinite Decimals
- Percents
- Portion of the Whole
- Things to Do with Real Numbers
- Addition and Subtraction of Real Numbers
- Properties of Addition
- Subtraction
- Multiplication
- Division
- Long Division Remainder
- Exponents and Powers - Whole Numbers
- Properties of Exponents
- Prime Factorization
- Order of Operations
- Even and Odd Numbers
- Infinity
- Sequences
- is Irrational
- Counting Rational Numbers
- Counting Real Numbers?
- Counting Irrational Numbers
- In the Real World
- Decimals in Use
- How to Solve a Math Problem
- I Like Abstract Things: Summary

We'll tell you what the main idea is. We use numbers to solve problems. A simple problem such as "If Ellen has 3 walls on which to watch the paint dry, and she watches 1 of them, how many walls are left to watch?" has a simple answer. As problems get more interesting, as surely they must, so do the numbers we need in order to solve them.

We'll go over each and every one of the main types of numbers you'll need in an algebra class. We'll cover natural numbers, whole numbers, integers, rational numbers, irrational numbers, and real numbers. We're going to skip over wrong numbers, because you can just hang up on them anyway.

We'll also talk about different ways to express the numbers we already *do* know, usually in the form of fractions, decimals, and percents. Because it can get boring to always write "1" as "1," and sometimes we just need to write it as 432,588 รท 432,588 to keep life interesting. Don't put that as the number of dependents on your 1040, though. The IRS tends to find such shenanigans unamusing. Lighten up, IRS.