Question

A basic cellular package costs $20 per month for 60 minutes of calling, with an additional charge of $0.20/min beyond that time. The cost formula would be C = 20 + 0.20(x − 60), where C is the cost measured in dollars and x is the number of calling minutes used. If you cannot have a bill greater than $60, what is the maximum number of calling minutes you can use?

Answer 1

Answer: you can use 260 min, 60 min at a fixed price ($20) and extra 200.

Step-by-step explanation:

C(x) = 20 + 0.20(x − 60)

C(x) ≤ 60

20 + 0.20(x − 60) ≤ 60

0.20(x − 60) ≤ 60 - 20

0.20x - 12 ≤ 40

0.20x ≤ 40 + 12

0.20x ≤ 52

x ≤ 52/0.2

x ≤ 260

This way, you can use 260 min, 60 min at a fixed price ($20) and extra 200.