standard_description: Construct a function to model a linear relationship between two quantities. Determine the rate of change and initial value of the function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. Interpret the rate of change and initial value of a linear function in terms of the situation it models, and in terms of its graph or a table of values.
problem_activity: Task
Katy is told that the cost of producing $x$ DVDs is given by $C(x) = 1.25x + 2500.$ She is then asked to find an equation for $\frac{C(x)}{x}$, the average cost per DVD of producing $x$ DVDs.
She begins her work: $$\frac{C(x)}{x} =\frac {1.25x+2500}{x}$$ and finishes by simplifying both sides to get: $$C = 1.25+\frac{2500}{x}$$  Is Katy's answer correct? Explain.


aligns: no