Prepaid Phone Card: Remaining Credit Calculation

How can we calculate the remaining credit on a prepaid phone card after a certain number of minutes of calls?

Shen purchased a prepaid phone card for $35.75. Calls cost 6 cents a minute using this card. The credit, C (in dollars), left on the card after it is used for x minutes of calls is given by the following function:

C(x) = 35.75 - 0.06x

Calculation Method

To calculate the remaining credit on a prepaid phone card after a certain number of minutes of calls, we can use the provided function C(x) = 35.75 - 0.06x, where:

- 35.75 represents the initial credit on the phone card.

- 0.06x represents the cost of the calls made, where 0.06 is the cost per minute and x is the number of minutes used.

By substituting the specific number of minutes into the function, we can determine the remaining credit on the card.

Detailed Explanation

When Shen purchased the prepaid phone card for $35.75, the initial credit on the card was $35.75. Each call costs 6 cents a minute, which is represented by 0.06x in the function.

Let's take an example: If Shen uses the card for 10 minutes, we can calculate the remaining credit by substituting x = 10 into the function:

C(10) = 35.75 - 0.06(10) = 35.75 - 0.6 = 35.15

Therefore, after using the card for 10 minutes, there would be $35.15 credit left on the card.

This calculation method helps in determining the remaining credit on the prepaid phone card after any given number of minutes of calls.