unknown
A variable in an equation that needs to be solved for.
A variable in an equation that has to be solved for.
A variable (usually
Examples of unknown in the following topics:

Equations and Inequalities
 Equations often express relationships between given quantities—the knowns—and quantities yet to be determined—the unknowns.
 The process of expressing the unknowns in terms of the knowns is called solving the equation.
 In an equation with a single unknown, a value of that unknown for which the equation is true is called a solution or root of the equation.
 In a set of simultaneous equations, or system of equations, multiple equations are given with multiple unknowns.
 A solution to the system is an assignment of values to all the unknowns so that all of the equations are true.

Introduction to Variables
 Variables are used in mathematics to denote arbitrary or unknown numbers.
 The last one, $x$, represents the solution of the equation, which is unknown and must be solved for.
 A number on its own (without an unknown variable) is called a constant; in this case, $d$ represents a constant.
 Therefore, a term may simply be a constant or a variable, or it may include both a coefficient and an unknown variable.
 In this case, $b$ is an unknown variable, not a parameter of the equation.

Estimating the Target Parameter: Interval Estimation
 Interval estimation is the use of sample data to calculate an interval of possible (or probable) values of an unknown population parameter.
 Interval estimation is the use of sample data to calculate an interval of possible (or probable) values of an unknown population parameter.
 How can we construct a confidence interval for an unknown population mean $\mu$ when we don't know the population standard deviation $\sigma$?
 These are both unknown parameters.
 First, draw a simple random sample from a population with an unknown mean.

Solving Equations: Addition and Multiplication Properties of Equality
 Equations often express relationships between given quantities ("knowns") and quantities yet to be determined ("unknowns").
 The process of expressing an equation's unknowns in terms of its knowns is called solving the equation.
 In an equation with a single unknown, a value of that unknown for which the equation is true is called a solution or root of the equation.
 Let $x$ equal the unknown value: the number of hours of labor.
 To solve for the unknown, first undo the addition operation (using the subtraction property) by subtracting $339 from both sides of the equation:

AcidBase Titrations
 Acidbase titration can determine the concentrations of unknown acid or base solutions.
 This lets us quantitatively analyze the concentration of the unknown solution.
 Rinse the burette with the standard solution, the pipette with the unknown solution, and the conical flask with distilled water.
 At this stage, we want a rough estimate of the amount of known solution necessary to neutralize the unknown solution.
 The solution in the flask contains an unknown number of equivalents of base (or acid).

Problem Solving
 Typically, you are given enough parameters to calculate the unknown.
 Choose a relevant gas law equation that will allow you to calculate the unknown variable.
 Calculate the unknown variable.
 Write down all the information that you know about the gas: P1 = 170 kPa and P2 is unknown.
 Calculate the unknown variable:

The Law of Sines
 The law of sines can be used to find unknown angles and sides in any triangle.
 To find an unknown side, we need to know the corresponding angle and a known ratio.
 The last unknown side is $b$, and we will follow a similar process for this.
 The angle $\beta$ and the sidelengths $b$ and $c$ are unknown.

The Central Limit Theorem for Sums
 Suppose X is a random variable with a distribution that may be known or unknown (it can be any distribution) and suppose:

Student Learning Outcomes
 Conduct and interpret hypothesis tests for a single population mean, population standard deviation unknown.

Student Learning Outcomes
 Conduct and interpret hypothesis tests for two population means, population standard deviations unknown.