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 18.1 Know Your Numbers 18.2 Order of Operations 18.3 Odd and Even Numbers 18.4 The Positive, the Negative, and the Ugly 18.5 Divisibility and Remainders 18.6 Factors 18.7 Multiples 18.8 Know Your Fractions

 18.9 Decimals 18.10 Percents 18.11 Ratios 18.12 Exponents 18.13 Roots and Radicals 18.14 Sequences 18.15 Sets
The SAT loves to throw around terminology about numbers. If you don’t know the terminology, you won’t know how to answer the question.
• Whole Numbers. The set of counting numbers, including zero {0, 1, 2, 3, . . .}.
• Natural Numbers. The set of all whole positive numbers except zero {1, 2, 3, 4, 5, . . .}.
• Integers. The set of all positive and negative whole numbers, including zero. Fractions and decimals are not included {. . . , –3, –2, –1, 0, 1, 2, 3, . . .}.
• Rational Numbers. The set of all numbers that can be expressed as integers in fractions. That is, any number that can be expressed in the form mn, where m and n are integers.
• Irrational Numbers. The set of all numbers that cannot be expressed as integers in a fraction. Examples include π, , and 1.01001000100001000001. . . . A number must be either rational or irrational; no number can be both.
• Real Numbers. Every number on the number line. The set of real numbers includes all rational and irrational numbers.
 Jump to a New ChapterIntroductionThe Discipline of DisciplineSAT StrategiesThe SAT Personal TrainerMeet the Writing SectionBeat the EssayBeat Improving SentencesBeat Identifying Sentence ErrorsBeat Improving ParagraphsMeet the Critical Reading sectionBeat Sentence CompletionsReading Passages: The Long and Short of ItThe Long of ItThe Short of ItSAT VocabularyMeet the Math SectionBeat Multiple-Choice and Grid-InsNumbers and OperationsAlgebraGeometryData, Statistics, and Probability
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