# A

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absolute value
The distance a number is from zero on the number line. For example -5 is 5 units away from zero. It would be written as |-5|

acute angle
An angle whose measure is less than 90 degrees

The operation, or process, of calculating the sum of two numbers or quantities

The number that when added to the original number will result in a sum of zero

Two angles that share a ray, thereby being directly next to each other

affine cipher
Affine ciphers use linear functions to scramble the letters of secret messages

algorithm
Step-by-step procedure by which an operation can be carried out

alternate exterior angles
Angles located outside a set of parallel lines and on opposite sides of the transversal

alternate interior angles
Angles located inside a set of parallel lines and on opposite sides of the transversal

angle bisector
A ray that divides an angle into two congruent angles

area
The number of square units needed to cover a surface

arithmetic mean
See mean

associative property
This property applies both to multiplication and addition and states that you can group several numbers that are being added or multiplied (not both) in any way and yield the same value. In mathematical terms, for all real numbers a, b, and c, (a+b)+c=a+(b+c) or (ab)c=a(bc)

average
It is better to avoid this sometimes vague term. It usually refers to the (arithmetic) mean, but it can also signify the median, the mode, the geometric mean, and weighted mean, among other things

average expected payoff
An estimate of the amount that will be gained in a game of chance, calculated by multiplying the probability of winning by the number of points won each time

axioms of probability
There are three axioms of probability: 1) The probability of an event is a real number greater than or equal to zero; 2) The sum of the probabilities of all possible outcomes of a given experiment is 1; 3) If two events cannot both occur at the same time, the chance that either one occurs is the sum of the chances that each occurs.