Question

1. the roaming cell phone company charges an initial fee of $15.00 plus $0.20 per minute of airtime usage. if juanita uses x minutes of airtime, what is an equation that can be used to determine the cost of her phone bill (c)?

a) c = 0.20 + 15x
b) c = 15 (0.20x)
c) c = 15 + x + 0.20
d) c = 15 + 0.20x

Explanation:

Step1: Identify fixed and variable costs

The initial fee of $15 is a fixed - cost and does not depend on the number of minutes. The cost per minute is $0.20 and it depends on the number of minutes $x$.

Step2: Form the cost equation

The total cost $C$ is the sum of the fixed cost and the variable cost. The variable cost is $0.20x$ (cost per minute times the number of minutes) and the fixed cost is 15. So the equation is $C = 15+0.20x$.

Answer:

d) $C = 15 + 0.20x$