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 40 minutes of calls is

Question 1155874: 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 40 minutes of calls is $15.20, and the remaining credit after 72 minutes of calls is $11.36. What is the remaining credit after 86 minutes of calls?
Answer by ikleyn(52787) (Show Source): You can put this solution on YOUR website!
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72 - 40 = 32 minutes of the phone call cost  15.20-11.36 = 3.84 dollars, giving the rate of   = 0.12 dollars per minute.


So, after 86 minutes the amount on the card will be  15.20 - (86-40)*0.12 = 9.68 dollars.

Solved.

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