Which situations represent linear functions? Check all that apply.

The temperature rises and falls over the course of a day. Temperature is a function of time.
A baseball is hit into the outfield. The height of the ball is a function of time.
A car goes 55 mph on the highway. Distance is a function of time.
A child grew 2 inches this year and 1 inch last year. Height is a function of time.
A movie director makes 2 movies per year. The number of movies is a function of the years.

1 answer

To determine which situations represent linear functions, we need to assess whether the relationship between the two variables can be described with a linear equation (i.e., in the form \(y = mx + b\), where \(m\) is a constant rate of change).

  1. The temperature rises and falls over the course of a day. Temperature is a function of time.

    • Not linear: The temperature typically varies in a non-linear manner (e.g., it might rise in the afternoon and drop at night).
  2. A baseball is hit into the outfield. The height of the ball is a function of time.

    • Not linear: The height of the ball follows a parabolic trajectory, which means it is quadratic, not linear.
  3. A car goes 55 mph on the highway. Distance is a function of time.

    • Linear: The distance traveled over time can be expressed as \(d = 55t\). This is a linear relationship.
  4. A child grew 2 inches this year and 1 inch last year. Height is a function of time.

    • Not linear: The growth does not occur at a constant rate each year in this scenario, making it a variable change.
  5. A movie director makes 2 movies per year. The number of movies is a function of the years.

    • Linear: The number of movies can be expressed as \(m = 2t\) (where \(t\) is the number of years). This is a linear relationship.

Based on this analysis, the situations that represent linear functions are:

  • A car goes 55 mph on the highway. Distance is a function of time.
  • A movie director makes 2 movies per year. The number of movies is a function of the years.