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 28 minutes of calls is

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Question 1117903: 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 28 minutes of calls is $26.08 , and the remaining credit after 61 minutes of calls is $21.46. What is the remaining credit after 88 minutes of calls?
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52908)   (Show Source): You can put this solution on YOUR website!
.
The rate per minute is   = 0.14 dollars.


Now subtract from $21.46 the cost of 88-61 minutes:


    21.46 - (88-61)*0.14 = 17.68.


Answer. $17.68.


Answer by greenestamps(13215)   (Show Source): You can put this solution on YOUR website!


The number of additional minutes between the two given points is 61-28=33. The difference in the remaining balance on the phone card is $26.08-$21.46 = $4.62.

The charge per minute for using the phone card is $4.62/33 = $0.14.

For 27 more minutes, the remaining balance will decrease by 27($0.14) = $3.78, leaving a balance of $21.46-$3.78 = $17.68.
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