Know Your Numbers
Know Your Numbers
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.
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