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Mathematical
Conventions
for the Quantitative Reasoning
Measure of the GRE® revised
General Test
Overview
The mathematical symbols and terminology used in the Quantitative Reasoning measure of the test are
conventional at the high school level, and most of these appear in the Math Review. Whenever
nonstandard or special notation or terminology is used in a test question, it is explicitly introduced in the
question. However, there are some particular assumptions about numbers and geometric figures that are
made throughout the test. These assumptions appear in the test at the beginning of the Quantitative
Reasoning sections, and they are elaborated below.
Also, some notation and terminology, while standard at the high school level in many countries, may be
different from those used in other countries or from those used at higher or lower levels of mathematics.
Such notation and terminology are clarified below. Because it is impossible to ascertain which notation
and terminology should be clarified for an individual test taker, more material than necessary may be
included.
Finally, there are some guidelines for how certain information given in test questions should be
interpreted and used in the context of answering the questions—information such as certain words,
phrases, quantities, mathematical expressions, and displays of data. These guidelines appear at the end.
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GRE are registered trademarks of Educational Testing Service (ETS).
Numbers and quantities
• All numbers used in the test questions are real numbers. In particular, integers and both rational and
irrational numbers are to be considered, but imaginary numbers are not. This is the main
assumption regarding numbers. Also, all quantities are real numbers, although quantities may
involve units of measurement.
• Numbers are expressed in base 10 unless otherwise noted, using the 10 digits 0 through 9 and a
period to the right of the ones digit, or units digit, for the decimal point. Also, in numbers that are
1,000 or greater, commas are used to separate groups of three digits to the left of the decimal point.
• When a positive integer is described by the number of its digits, e.g., a two-digit integer, the digits
that are counted include the ones digit and all the digits further to the left, where the left-most digit
is not 0. For example, 5,000 is a four-digit integer, whereas 031 is not considered to be a three-digit
integer.
• Some other conventions involving numbers: one billion means 1,000,000,000, or 910 (not 1210 , as
in some countries); one dozen means 12; the Greek letter p represents the ratio of the
circumference of a circle to its diameter and is approximately 3.14.
• When a positive number is to be rounded to a certain decimal place and the number is halfway
between the two nearest possibilities, the number should be rounded to the greater possibility. For
example, 23.5 rounded to the nearest integer is 24, and 123.985 rounded to the nearest 0.01 is
123.99. When the number to be rounded is negative, the number should be rounded to the lesser
possibility. For example, 36.5- rounded to the nearest integer is 37.-
• Repeating decimals are sometimes written with a bar over the digits that repeat, as in 25 2.08312 =
and 1 0.142857.7 =
• If r, s, and t are integers and ,rs t= then r and s are factors, or divisors, of t; also, t is a multiple of
r (and of s) and t is divisible by r (and by s). The factors of an integer include positive and negative
integers. For example, 7- is a factor of 35, 8 is a factor of 40,- and the integer 4 has six factors:
4,- 2,- 1,- 1, 2, and 4. The terms factor, divisor, and divisible are used only when r, s, and t are
integers. However, the term multiple can be used with any real numbers s and t provided r is an
integer. For example, 1.2 is a multiple of 0.4, and 2p- is a multiple of p .
• The least common multiple of two nonzero integers a and b is the least positive integer that is a
multiple of both a and b. The greatest common divisor (or greatest common factor) of a and b is the
greatest positive integer that is a divisor of both a and b.
• If an integer n is divided by a nonzero integer d resulting in a quotient q with remainder r, then
, where n qd r= + 0 .r d Furthermore, 0=r if and only if n is a multiple of d. For
example, when 20 is divided by 7, the quotient is 2 and the remainder is 6; when 21 is divided by 7,
the quotient is 3 and the remainder is 0; and when 17- is divided by 7, the quotient is 3- and the
remainder is 4.
£ <
• A prime number is an integer greater than 1 that has only two positive divisors: 1 and itself. The
first five prime numbers are 2, 3, 5, 7, and 11. A composite number is an integer greater than 1 that
is not a prime number. The first five composite numbers are 4, 6, 8, 9, and 10.
• Odd and even integers are not necessarily positive; for example, 7- is odd, and 18- and 0 are
even.
• The integer 0 is neither positive nor negative.
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Mathematical expressions, symbols, and variables
• As is common in algebra, italic letters like x are used to denote numbers, constants, and variables.
Letters are also used to label various objects, such as line ,A point P, function f, set S, list T, event
E, random variable X, Brand X, City Y, and Company Z. The meaning of a letter is determined by
the context.
• When numbers, constants, or variables are given, their possible values are all real numbers unless
otherwise restricted. It is common to restrict the possible values in various ways. Here are some
examples: n is a nonzero integer; 1 ;p£
o The measures of angles BAD and BDA are equal.
o The measure of angle DBC is less than x degrees.
o The area of triangle ABD is greater than the area of triangle DBC.
o Angle SRT is a right angle.
o Line m is parallel to line AC.
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Coordinate systems
• Coordinate systems, such as xy-planes and number lines, are drawn to scale. Therefore, you can
read, estimate, or compare quantities in such figures by sight or by measurement, including
geometric figures that appear in coordinate systems.
• The positive direction of a number line is to the right.
• As in geometry, distances in a coordinate system are nonnegative.
• The rectangular coordinate plane, or rectangular coordinate system, commonly known as the xy-
plane, is shown below. The x-axis and y-axis intersect at the origin O, and they partition the plane
into four quadrants. Each point in the xy-plane has coordinates ( ),x y that give its location with
respect to the axes; for example, the point ( )2, 8-P is located 2 units to the right of the y-axis and 8
units below the x-axis. The units on the x-axis have the same length as the units on the y-axis,
unless otherwise noted.
• Intermediate grid lines or tick marks in a coordinate system are evenly spaced unless otherwise
noted.
• The term x-intercept refers to the x-coordinate of the point at which a graph in the xy-plane
intersects the x-axis. The term y-intercept is used analogously. Sometimes the terms x-intercept and
y-intercept refer to the actual intersection points.
Sets, lists, and sequences
• Sets of numbers or other elements appear in some questions. Some sets are infinite, such as the set
of integers; other sets are finite and may have all of their elements listed within curly brackets, such
as the set { }2, 4, 6, 8 . When the elements of a set are given, repetitions are not counted as
additional elements and the order of the elements is not relevant. Elements are also called members.
A set with one or more members is called nonempty; there is a set with no members, called the
empty set and denoted by .∆ If A and B are sets, then the intersection of A and B, denoted by
,«A B is the set of elements that are in both A and B, and the union of A and B, denoted by
,»A B is the set of elements that are in A or B, or both. If all of the elements in A are also in B,
then A is a subset of B. By convention, the empty set is a subset of every set. If A and B have no
elements in common, they are called disjoint sets or mutually exclusive sets.
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• Lists of numbers or other elements are also used in the test. When the elements of a list are given,
repetitions are counted as additional elements and the order of the elements is relevant. For
example, the list 3, 1, 2, 3, 3 contains five numbers, and the first, fourth, and last numbers in the list
are each 3.
• The terms data set and set of data are not sets in the mathematical sense given above. Rather they
refer to a list of data because there may be repetitions in the data, and if there are repetitions, they
would be relevant.
• Sequences are lists that often have an infinite number of elements, or terms. The terms of a
sequence are often represented by a fixed letter along with a subscript that indicates the order of a
term in the sequence. For example, represents an infinite sequence in which
the first term is 1,a the second term is 2,a and more generally, the nth term is na for every positive
integer n. Sometimes the nth term of a sequence is given by a formula, such as 2 1= +
Sometimes the first few terms of a sequence are given explicitly, as in the following sequence of
consecutive even negative integers: . . . .
1 2 3, , , . . . , , . . .na a a a
2, 4, 6, 8, 10,- - - - -
.nnb
• Sets of consecutive integers are sometimes described by indicating the first and last integer, as in
“the integers from 0 to 9, inclusive.” This phrase refers to 10 integers, with or without “inclusive”
at the end. Thus, the phrase “during the years from 1985 to 2005” refers to 21 years.
Data and statistics
• Numerical data are sometimes given in lists and sometimes displayed in other ways, such as in
tables, bar graphs, or circle graphs. Various statistics, or measures of data, appear in questions:
measures of central tendency—mean, median, and mode; measures of position—quartiles and
percentiles; and measures of dispersion—standard deviation, range, and interquartile range.
• The term average is used in two ways, with and without the qualification “(arithmetic mean).” For
a list of data, the average (arithmetic mean) of the data is the sum of the data divided by the number
of data. The term average does not refer to either median or mode in the test. Without the
qualification of “arithmetic mean,” average can refer to a rate or the ratio of one quantity to
another, as in “average number of miles per hour” or “average weight per truckload.”
• When mean is used in the context of data, it means arithmetic mean.
• The median of an odd number of data is the middle number when the data are listed in increasing
order; the median of an even number of data is the arithmetic mean of the two middle numbers
when the data are listed in increasing order.
• For a list of data, the mode of the data is the most frequently occurring number in the list. Thus,
there may be more than one mode for a list of data.
• For data listed in increasing order, the first quartile, second quartile, and third quartile of the data
are three numbers that divide the data into four groups that are roughly equal in size. The first group
of numbers is from the least number up to the first quartile. The second group is from the first
quartile up to the second quartile, which is also the median of the data. The third group is from the
second quartile up to the third quartile, and the fourth group is from the third quartile up to the
greatest number. Note that the four groups themselves are sometimes referred to as quartiles—first
quartile, second quartile, third quartile, and fourth quartile. The latter usage is clarified by the
word “in” as in the phrase “the cow’s weight is in the third quartile of the weights of the herd.”
• For data listed in increasing order, the percentiles of the data are 99 numbers that divide the data
into 100 groups that are roughly equal in size. The 25th percentile equals the first quartile; the 50th
percentile equals the second quartile, or median; and the 75th percentile equals the third quartile.
• For a list of data, where the arithmetic mean is denoted by m, the standard deviation of the data
refers to the nonnegative square root of the mean of the squared differences between m and each of
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the data. This statistic is also known as the population standard deviation and is not to be confused
with the sample standard deviation.
• For a list of data, the range of the data is the greatest number in the list minus the least number. The
interquartile range of the data is the third quartile minus the first quartile.
Data distributions and probability