Question

The function f(x) = 0.11x + 43 relates how much Derek pays for phone service, f(x), to the number of minutes, x, used for international calls in a month. What is the value and meaning of f(320)?
A:$78.20; this is the amount Derek pays for 320 months of service.
B:$78.20; this is the amount Derek pays for 320 minutes of international calls.
C: $92.50; this is the amount Derek pays for 320 months of service.
D:$92.50; this is the amount Derek pays for 320 minutes of international calls.

Answer 1

The answer is B. $78.20; this is the amount Derek pays for 320 minutes of international calls.

Simply substitute in 320 wherever there is an x and solve. The problem also already told us that x stands for minutes so we know it is 320 minutes.