Question

A municipal electrical utility charges customers a $15 per month fee plus 12 cents per kilowatt- hour of energy used.

Write an equation for a customer's monthly costs, C (in dollars) for electric service as a function of r, the kilowatt-hours used.

a.C(x) 12 + 0.15x

b.C(z) = 15e0.12z

c.C(x) = 15 + 12z

d.C(z) = 15 + 0.12c

e.C(z)= 15(1.12)"

Answer 1

`C(r)=15+0.12r`

No option is correct.

Explanation:

Modeling With Functions

The customer's monthly costs C expressed in dollars has two parts: one fixed cost regardless of the energy used ($15) and a variable cost (12 cents per kilowatt-hours). This can be expressed as 12/100*r = 0.12 r, being r the kilowatt-hours used. Joining both parts, we get the total cost expression as

`C(r)=15+0.12r`

From the options presented, none of them can be called as correct, only the option d. is close enough to the real answer, but the variables z and c used are not accurate.