Chapter 13

# Ten Essential Math Concepts

IN THIS CHAPTER

**Appreciating how simple concepts are indispensable in math**

**Seeing why π and prime numbers are important**

**Understanding the importance of graphs and functions**

**Looking at the world of real numbers**

Math itself is one big concept, and it’s chock full of so many smaller concepts that no one person can possibly understand them all. However, certain concepts get so much airplay that, in my humble opinion, they make the Math Hall of Fame. So here’s my list of the ten most important concepts in mathematics.

## Playing with Prime Numbers

A *prime number* is any counting number that has exactly two divisors (numbers that divide into it evenly) — 1 and the number itself. Here are the first ten prime numbers:

2 3 5 7 11 13 17 19 23 29 …

Prime numbers go on forever — that is, the list is infinite. Beyond this, prime numbers are, in an important sense, the elements from which all other numbers can be built. Every counting number greater than 1, no matter how large, can be written as the unique product of prime numbers. See Chapter 1 for more on ...

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