Direct Variation Models (11:11)

- Describe direct variation.
- What is the formula for direct variation? What does \begin{align*}k\end{align*} represent?

Translate the following direct variation situations into equations. Choose appropriate letters to represent the varying quantities.

- The amount of money you earn is directly proportional to the number of hours you work.
- The weight of an object on the Moon varies directly with its weight on Earth.
- The volume of a gas is directly proportional to its temperature in Kelvin.
- The number of people served varies directly with the amount of ground meat used to make burgers.
- The amount of a purchase varies directly with the number of pounds of peaches.

Explain why each equation is not an example of direct variation.

- \begin{align*}\frac{4}{x}=y\end{align*}
- \begin{align*}y=9\end{align*}
- \begin{align*}x=-3.5\end{align*}
- \begin{align*}y=\frac{1}{8} x+7\end{align*}
- \begin{align*}4x+3y=1\end{align*}