#### Average

Add $n$ numbers and divide the result by $n$.

#### Associative Property of Multiplication

When three real numbers are multiplied, it makes no difference which two are multiplied first.

#### Associative Property of Addition

When three real numbers are added, it makes no difference which two are added first.

#### Area formula

A formula used to find the area of geometric objects or figures. Area is measured in square units.

#### Approximately equal to

The symbol $\,\approx\,$ represents an answer that is rounded to a specified number of decimal places.

#### Alternative rule for subtracting two fractions

If $a$, $b$, $c$, and $d$ are integers with $b\ne 0$ and $d\ne 0$, then $\,\displaystyle{a\over b}-{c\over d}={{ad-bc}\over{bd}}$.

#### Alternative rule for adding two fractions

If $a$, $b$, $c$, and $d$ are integers with $b\ne 0$ and $d\ne 0$, then $\,\displaystyle{a\over b}+{c\over d}={{ad+bc}\over{bd}}$.

#### Algebraic inequality

An inequality that contains one or more variable terms.

#### Algebraic expression

A collection of variables and constants combined by using addition, subtraction, multiplication, or division.

#### Algebraic equation

Uses an equal sign to set two algebraic expressions equal to each other and is true for only certain values of the variable.

#### Additive Inverse Property

The sum of a real number and its opposite is zero.

#### Additive Inverse

Two numbers whose sum is zero.

#### Additive Identity Property

The sum of zero and a real number equals the number itself.

#### Addition Property of Inequalities

Add the same quantity to each side.

#### Adding fractions with unlike denominators

Rewrite the fractions so that they have like denominators. Then use the rule for adding fractions with like denominators.

#### Adding fractions with like denominators

Let $a$, $b$, and $c$ be integers with $c\ne0$. Then use the following rule: $\displaystyle{a\over c}+{b\over c}={{a+b}\over{c}}$

#### Add two integers with unlike signs

Find the absolute value of each integer. Subtract the lesser absolute value from the greater absolute value and attach the sign of the integer with the greater absolute value.

#### Add two integers with like signs

Add their absolute values and attach the common sign to the result.

#### Abundant number

A number where the sum of its proper factors is greater than the number.

#### Absolute value

The distance between any real number and 0 on the real number line.