2. Direct Variation
◦ Describes the relationship between two variables who either both increase or both decrease
◦ As one variable increases, so does the other
◦ As one variable decreases, so does the other
◦ As the temperature goes up, so does my electric bill because I pay for AC
◦ As I make more money, more taxes are taken out of my paycheck
3. Inverse Variation
◦ Describes the relationship between two variables who behave in opposite ways
◦ As one variable increases, the other variable decreases
◦ As one variable decreases, the other variable increases
◦ The less gas that is available in the United States, the more each gallon costs
◦ As the number of people in a room increases, the amount of oxygen to breathe decreases
4. The variables x and y are directly
proportional to one another. If x = 4
when y = 12, find y when x = 8.
◦ x/y = x/y
◦ 4/12 = 8/y
◦ 4y = 96
◦ y = 24
5. The variables x and y are inversely
proportional to one another. If x = 4
when y = 12, find y when x = 8.
◦ xy = xy
◦ 4(12) = 8y
◦ 48 = 8y
◦ y = 6
