Answer:
The total number of minutes is 87 minutes.
Step-by-step 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 ([tex]C(t)[/tex]), measured in euros, minus a fixed cost ([tex]C_{o}[/tex]), measured in euros, and is directly proportional to total time ([tex]t[/tex]), measured in minutes. That is:
[tex]C(t) - C_{o} \propto t[/tex]
[tex]C(t) -C_{o} = r\cdot t[/tex]
[tex]C(t) = C_{o}+r\cdot t[/tex] (Eq. 1)
Where [tex]r[/tex] is the proportionality ratio, measured in euros per minute.
If we know that [tex]C_{o} = 14.99\,EUR[/tex], [tex]C(t) = 20.21\,EUR[/tex] and [tex]r = 0.06\,\frac{EUR}{min}[/tex], then the total number of minutes is:
[tex]20.21= 14.99+0.06\cdot t[/tex]
[tex]t = \frac{20.21-14.99}{0.06}[/tex]
[tex]t = 87\,min[/tex]
The total number of minutes is 87 minutes.
