Читать книгу Basic Math & Pre-Algebra All-in-One For Dummies (+ Chapter Quizzes Online) - Mark Zegarelli - Страница 20

In the preceding section, you see how a variety of number sequences extend infinitely. In this section, I provide a quick tour of how numbers fit together as a set of nested systems, one inside the other.

When I talk about a set of numbers, I’m really just talking about a group of numbers. You can use the number line to deal with four important sets of numbers.

 Counting numbers (also called natural numbers): The set of numbers beginning 1, 2, 3, 4 and going on infinitely

 Integers: The set of counting numbers, zero, and negative counting numbers

 Rational numbers: The set of integers and fractions

 Real numbers: The set of rational and irrational numbers

The sets of counting numbers, integers, rational, and real numbers are nested, one inside another. This nesting of one set inside another is similar to the way that a city (for example, Boston) is inside a state (Massachusetts), which is inside a country (the United States), which is inside a continent (North America). The set of counting numbers is inside the set of integers, which is inside the set of rational numbers, which is inside the set of real numbers.