SAT Study Guide/Part 2 - The Math Section/General Numerical Concepts

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Number properties[edit]

There are several sets of numbers:

  1. Counting or Natural numbers are numbers that can be used to count real things:
  2. Integers (including 0) include the natural numbers and their opposites:
    • Even integers are divisible by 2; you can express even integer as , where is any integer:
    • Odd integers are not divisible by 2; you can express any odd integer as , where is any integer:
  3. Rational numbers are numbers you can express as a fraction , where and cannot simplify the other:
  4. Irrational numbers are non-repeating, non-terminating decimals that you cannot express as a ratio or division of intergers , where and cannot simplify the other:
  5. Real numbers include all of the above.

Numbers can be prime. That is, they are divisible by themselves and one, only. 1 is not considered a prime number, and 2 is the only even prime number. The first eight prime numbers are: