GRE Quantitative Reasoning Prep exam
even + even = - even
even - even = - even
even + odd = - odd
even - odd = - odd
odd + odd = - even
odd - odd = - even
odd × odd = - odd
even × odd = - even
even × even = - even
,GRE Quantitative Reasoning Prep exam
least common multiple - the least positive integer that is a multiple of both a and
b. For example, the least common multiple of 30 and 75 is 150. This is because the
positive multiples of 30 are 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, etc., and
the positive multiples of 75 are 75, 150, 225, 300, 375, 450, etc. Thus, the
common positive multiples of 30 and 75 are 150, 300, 450, etc., and the least of
these is 150.
greatest common divisor (or greatest common factor) - the greatest positive
integer that is a divisor of both a and b. For example, the greatest common divisor
of 30 and 75 is 15. This is because the positive divisors of 30 are 1, 2, 3, 5, 6, 10,
15, and 30, and the positive divisors of 75 are 1, 3, 5, 15, 25, and 75. Thus, the
common positive divisors of 30 and 75 are 1, 3, 5, and 15, and the greatest of
these is 15.
prime number - an integer greater than 1 that has only two positive divisors: 1
and itself
first ten prime numbers - 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29
prime factorization - Every integer greater than 1 either is a prime number or can
be uniquely expressed as a product of factors that are prime numbers, or prime
divisors
,GRE Quantitative Reasoning Prep exam
composite number - An integer greater than 1 that is not a prime number
The first ten composite numbers - 4, 6, 8, 9, 10, 12, 14, 15, 16, and 18
add two fractions with the same denominator - add the numerators and keep the
same denominator. For example, - + = -8 + = -
add two fractions with different denominators - To add two fractions with
different denominators, first find a common denominator, which is a common
multiple of the two denominators. Then convert both fractions to equivalent
fractions with the same denominator. Finally, add the numerators and keep the
common denominator. So: 1/3 + -2/5 = 5/15 + -6/15 = -1/15
To multiply two fractions - multiply the two numerators and multiply the two
denominators. So: (10/7) (-1/3) = (10)(-1) / (7)(3) = -10/21
To divide one fraction by another - first invert the second fraction—that is, find its
reciprocal—then multiply the first fraction by the inverted fraction. So
(3/10)/(7/13) = (3/10)(13/7) = 39/70
, GRE Quantitative Reasoning Prep exam
negative number raised to even power = - positive
negative number raised to odd power = - negative
√a√b - √ab
(√a)^2 - a
√a^2 - a
√a/√b - √ab
interval - The set of all real numbers that are between, say, 5 and 8 is called an
interval, and the double inequality is often used to represent that interval: 5 < x <
8
ratio - The ratio of one quantity to another is a way to express their relative sizes,
often in the form of a fraction, where the first quantity is the numerator and the
second quantity is the denominator. Thus, if s and t are positive quantities, then
the ratio of s to t can be written as the fraction .st The notation "s to t" or "s : t" is
also used to express this ratio. For example, if there are 2 apples and 3 oranges in
even + even = - even
even - even = - even
even + odd = - odd
even - odd = - odd
odd + odd = - even
odd - odd = - even
odd × odd = - odd
even × odd = - even
even × even = - even
,GRE Quantitative Reasoning Prep exam
least common multiple - the least positive integer that is a multiple of both a and
b. For example, the least common multiple of 30 and 75 is 150. This is because the
positive multiples of 30 are 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, etc., and
the positive multiples of 75 are 75, 150, 225, 300, 375, 450, etc. Thus, the
common positive multiples of 30 and 75 are 150, 300, 450, etc., and the least of
these is 150.
greatest common divisor (or greatest common factor) - the greatest positive
integer that is a divisor of both a and b. For example, the greatest common divisor
of 30 and 75 is 15. This is because the positive divisors of 30 are 1, 2, 3, 5, 6, 10,
15, and 30, and the positive divisors of 75 are 1, 3, 5, 15, 25, and 75. Thus, the
common positive divisors of 30 and 75 are 1, 3, 5, and 15, and the greatest of
these is 15.
prime number - an integer greater than 1 that has only two positive divisors: 1
and itself
first ten prime numbers - 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29
prime factorization - Every integer greater than 1 either is a prime number or can
be uniquely expressed as a product of factors that are prime numbers, or prime
divisors
,GRE Quantitative Reasoning Prep exam
composite number - An integer greater than 1 that is not a prime number
The first ten composite numbers - 4, 6, 8, 9, 10, 12, 14, 15, 16, and 18
add two fractions with the same denominator - add the numerators and keep the
same denominator. For example, - + = -8 + = -
add two fractions with different denominators - To add two fractions with
different denominators, first find a common denominator, which is a common
multiple of the two denominators. Then convert both fractions to equivalent
fractions with the same denominator. Finally, add the numerators and keep the
common denominator. So: 1/3 + -2/5 = 5/15 + -6/15 = -1/15
To multiply two fractions - multiply the two numerators and multiply the two
denominators. So: (10/7) (-1/3) = (10)(-1) / (7)(3) = -10/21
To divide one fraction by another - first invert the second fraction—that is, find its
reciprocal—then multiply the first fraction by the inverted fraction. So
(3/10)/(7/13) = (3/10)(13/7) = 39/70
, GRE Quantitative Reasoning Prep exam
negative number raised to even power = - positive
negative number raised to odd power = - negative
√a√b - √ab
(√a)^2 - a
√a^2 - a
√a/√b - √ab
interval - The set of all real numbers that are between, say, 5 and 8 is called an
interval, and the double inequality is often used to represent that interval: 5 < x <
8
ratio - The ratio of one quantity to another is a way to express their relative sizes,
often in the form of a fraction, where the first quantity is the numerator and the
second quantity is the denominator. Thus, if s and t are positive quantities, then
the ratio of s to t can be written as the fraction .st The notation "s to t" or "s : t" is
also used to express this ratio. For example, if there are 2 apples and 3 oranges in
