Math definitions

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GMAT Study Guide - a prep wikibook


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No matter how brilliant you are, you need to know the conventions in the field. Math, and particularly GMAT math, has several conventions, definitions, and jargon terms. They are collected in this page.

Contents

Top quirks

This is a short list of truisms knowing which can save you from the most common errors:

  1. 0 is not positive, nor negative
  2. 0 is a multiple of every number, and therefore is even
  3. 0 and 1 are neither prime nor composite
  4. 0 is greater than -1
  5. is undefined
  6. 2 is the only even prime number

Number families

real  
all numbers on GMAT are real
integer  
{..., -3, -2, -1, 0, 1, 2, 3, ...}
fractional  
non-integer reals, such as 3.1417
whole  
{0, 1, 2, 3, ...}
even  
{..., -4, -2, 0, 2, 4 ...}
odd  
{..., -3, -1, 1, 3, ...}
positive  
any number strictly greater than zero
negative  
any number strictly less than zero
perfect squares  
{1, 4, 9, 16, ...} - integer squares of other integers
prime  
{2, 3, 5, 7, 11, 13, ...} - see below for a definition
composite  
{4, 6, 8, 9, ..} - non-prime positive integers except 1

Factors and multiples

Suppose (all numbers are whole). Then:

  1. is a multiple of and of
  2. and are divisors (factors) of

Prime and composite numbers

The positive integer () is a prime if the only positive divisors of are 1 and itself. The first 10 primes are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29. All other positive integers (except 1) that are not prime are composite numbers.

See also Prime test.

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