Question

Alan purchased a prepaid phone card for $40.25. Calls cost 9 cents per min using the card. The credit, C (in dollars), left on the card after it is used for x min of calls is given by the following function.C(x)=40.25-0.09xHow much credit is left on the card after 15 min of calls?

Answer 1

We have the function that models the credit C left on the card:

`C(x)\text{ = 40.25 -0.09x}`

x is the total of mins of calls.

If Alan calls for 15 mins, we have to find the left on the card.

So x = 15 because is the amount of mins.

Replace and solve:

`C(x)\text{ = 40.25-0.09(15)}`
`C(x)\text{ = 40.25-1.35}`
`C(x)\text{ = 38.9}`

So, $38.9 is the amount of credit left on the card.