Question

Jane has a pre-paid cell phone with NextFell. 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 370 minutes and the cost was $133.00. In July she used 530 minutes and the cost was $181.00.
A) Express the monthly cost C
C
in terms of x
x
, the number of minutes of calling time she used.
Answer: c

B) If Jane used 477 minutes of calling time in August, how much was her bill?
Answer: $

Answer 1

Answer:

• C = 0.30x +22
• $165.10

Step-by-step explanation:

A) Let x represent minutes used, and C represent monthly charge. We are given two (x, C) pairs: (370, 133.00) and (530, 181.00)

We can use these in the 2-point form of the equation for a line.

  y = (y2 -y1)/(x2 -x1)(x -x1) +y1

  C = (181 -133)/(530 -370)(x -370) +133

  C = 48/160(x -370) +133

  C = 0.30x -111 +133

  C = 0.30x +22

__

B) For x = 477 minutes, the charge will be ...

  C = 0.30(477) +22 = $165.10 . . . . for 477 minutes