Question 1200356: Jane has a pre-paid cell phone with Splint. 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 130 minutes and the cost was $76.50. In July she used 510 minutes and the cost was $209.50.
A) Express the monthly cost as C as a function of X, the number of minutes of calling time she used.
Answer:
B) If Jane used 205 minutes of calling time in August, how much was her bill?
Answer: $
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617)   (Show Source):
You can put this solution on YOUR website! "Splint" cell phone plan? A repeat question from several days ago?
Look for points, (x,y) for x minutes, y cost.
(130, 76.5) and (510, 209.5) They are on a line. You know what to do.
Answer by ikleyn(52786)  (Show Source):
You can put this solution on YOUR website! .
Jane has a pre-paid cell phone with Splint. 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 130 minutes and the cost was $76.50.
In July she used 510 minutes and the cost was $209.50.
A) Express the monthly cost as C as a function of X, the number of minutes of calling time she used.
B) If Jane used 205 minutes of calling time in August, how much was her bill?
~~~~~~~~~~~~~~~~~~~~~~~
The difference in the cost, 209.50 - 76.50 = 133 dollars, is due to the difference of minutes
510 - 130 = 380 minutes.
Hence, each minute costs  = 0.35 dollars.
Now we can compute the monthly fee. It is 76.50 - 130*0.35 = 31.00 dollars,
from the June's bill.
Hence, the cost function is C(X) = 31 + 0.35*X.
It is your ANSWER to question (A).
To answer question (B), you should calculate
C(205) = 31 + 0.35*205 = 102.75 dollars.
It is the ANSWER to question (B).
Solved.
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