Sarah plans to sell homemade birdhouses at the local craft fair. She spent 90 dollars on new tools and estimates that she spends 6 dollars in materials for each birdhouse. Which rational function models the average cost per birdhouse, y , in dollars of building x birdhouses?
Answer
A
y is equal to 90 over x
B
y is equal to the fraction with numerator 90 plus 6 x and denominator x
C
y is equal to 90 over 6 x
D
y is equal to the fraction with numerator 90 times open paren x plus 6 close paren and denominator x
Explanation
The total cost includes the $90 for tools plus $6 for each of x birdhouses, so the total is 90 + 6x dollars. Average cost per birdhouse is total cost divided by the number of birdhouses, giving y = (90 + 6x)/x. Therefore, the correct choice is B, the fraction with numerator 90 + 6x and denominator x.
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