In mathematics, you will frequently work with relationships among different quantities. A variable is used to represent these quantities. For example, consider the relationship between the mass of a substance and the volume of a substance.

One liter of crude oil has a mass of 0.827 kilograms, two liters of crude oil have a mass of 1.654 kilograms

The relationship between the mass of crude oil and the volume of crude oil is called a multiplicative relationship. For each barrel of crude oil, if you know the volume, V, in liters, you can calculate the mass, m, of the crude oil in kilograms by multiplying the volume by 0.827.

Oil is typically sold by volume, so in the relationship between mass and volume, volume is the independent variable, or the input variable that is used to make a calculation. Because the mass of the oil depends on the volume, mass is the dependent variable.

Another type of relationship is an additive relationship. An empty metal barrel of oil weighs about 40 pounds. One gallon of crude oil weighs 7.2 pounds.

an oil barrel with no oil weighs forty pounds, an oil barrel with one gallon of oil weighs 47.2 pounds, and an oil barrel with two gallons of oil weighs 54.4 pounds

In this lesson, you will use verbal descriptions, tables, graphs, and equations to represent both multiplicative and additive relationships. You will also use tables of data to write equations that relate the independent variable and the dependent variable.