A drawing that looks like a piece of tape, used to model expressions. Also called a bar model.

A sample that selects itself. For example, if you put an ad in the school paper asking for volunteers to take a survey, the students who respond will be a voluntary-response sample.

The absolute value of a number is its distance from 0 on the number line. Numbers that are the same distance from 0 have the same absolute value of 3.

A nmber for which the sum of all its proper factors is greater than the number itself. For example, 24 is an abundant number because the sum of its proper factor is 36; 1 + 2 + 3 + 4 + 6 + 8 + 12 = 36 [..]

An acute triangle is a triangle with three acute angles.

Zero is the additive identity for rational numbers. Adding zero to any rational number results in a sum identical to the original rational number. For any rational number a

Two numbers, a

Two angles in a plane that share a common vertex and common side but do not overlap are adjacent angles. In the parallelogram below, a

Two sides that meet at a vertex. In this rectangle, sides AB

A set of rules for performing a procedure. Mathematicians invent algorithms that are useful in many kinds of situations. Some examples of algorithms are the rules for long division or the rules for ad [..]