Question

sarah plans to sell homemade birdhouses at the local craft fair. she spent $90 on new tools and estimates that she spends $6 in materials for each birdhouse. which rational function models the average cost per birdhouse, y, in dollars of building x birdhouses?
○ $y = \frac{90}{x}$
○ $y = \frac{90(x + 6)}{x}$
○ $y = \frac{90 + 6x}{x}$
○ $y = \frac{90}{6x}$

Explanation:

Step1: Calculate total cost

Total cost = Fixed cost + Variable cost = $90 + 6x$

Step2: Find average cost

Average cost $y$ = $\frac{\text{Total Cost}}{\text{Number of birdhouses}}$ = $\frac{90+6x}{x}$

Answer:

$\boldsymbol{y=\frac{90+6x}{x}}$ (the third option)