Question

3. A cellular phone company offers a contract that costs 14.99€ plus 06€ per minute. Find the total number of minutes talked if the bill for October was 20.21€.

Answer 1

The total number of minutes is 87 minutes.

Explanation:

Correct statement is:

3. A cellular phone company offers a contract that costs 14.99 € plus 0.06 € per minute. Find the total number of minutes talked if the bill for October was 20.21 €.

From statement we know that total bill (
`C(t)`), measured in euros, minus a fixed cost (
`C_(o)`), measured in euros, and is directly proportional to total time (
`t`), measured in minutes. That is:

`C(t) - C_(o) \propto t`

`C(t) -C_(o) = r\cdot t`

`C(t) = C_(o)+r\cdot t` (Eq. 1)

Where
`r` is the proportionality ratio, measured in euros per minute.

If we know that
`C_(o) = 14.99\,EUR`,
`C(t) = 20.21\,EUR` and
`r = 0.06\,(EUR)/(min)`, then the total number of minutes is:

`20.21= 14.99+0.06\cdot t`

`t = (20.21-14.99)/(0.06)`

`t = 87\,min`

The total number of minutes is 87 minutes.