SOLUTION: The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after 31 minutes of calls is

Algebra ->  Equations -> SOLUTION: The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after 31 minutes of calls is       Log On


   

Question 1148636: The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after 31 minutes of calls is $16.28, and the remaining credit after 65 minutes of calls is $12.20. What is the remaining credit after 81 minutes of calls?
Answer by greenestamps(13198) About Me  (Show Source):
You can put this solution on YOUR website!


The additional cost of the additional 34 minutes is $4.08; the cost per minute is $4.08/34 = $0.12.

81 minutes is an additional 16 minutes past 65 minutes; the cost of the additional 16 minutes is 16*$0.12 = $1.92.

The credit remaining after 81 minutes is $12.20 - $1.92 = $10.28.