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 $78.20; / B.this is the amount Derek pays for 320 minutes of international calls $92.50; / C.this is the amount Derek pays for 320 months of service $92.50; / D. this is the amount Derek pays for 320 minutes of international calls

Answer 1

Given the function f(x) = 0.11x + 43, this shows the relationship between how much Derek has to pay for phone service for the amount of minutes he uses on international calls a month. 

f(320) can be solved by substituting x = 320, and this is shown below:

f(x) = 0.11x + 43
f(320) = 0.11(320) + 43
f(320) = 78.2

This means that Derek has to pay $78.20 for the 320 minutes of calls. Among the choices, the correct answer is B.