Question

Jane has a pre-paid cell phone with Ringular. She can't remember the exact costs, but her plan has a monthly fee and a charge for each minute of calling time. In June she used 230 minutes and the cost was $86.00. In July she used 730 minutes and the cost was $186.00.

A) Express the monthly cost
C
as a function of
x
, the number of minutes of calling time she used. Use function notation in your answer.

Answer 1

Answer:

C = 40+0.2x

Step-by-step explanation:

Let the monthly fee is $ a and per minute charge is $ b.

So, the cost function will be C = a+bx

when, x= 230 minutes given C = $86.00

So, 86 = a+b*230.

again, when x = 730 minutes given C = $186.00

so, 186 = a+b*730.

Taking difference of both equation we get,

b*500 = 100

or, b= 1/5 = 0.2

putting b=0.2 in first equation we get,

a + 0.2*230 = 86

or, a= 40

So, the cost function will be C = 40+0.2x