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For her phone service, Mai pays a monthly fee of $19, and she pays an additional $0.04 per minute of use. The least she has been charged in a month is$70.28. What are the possible numbers of minutes she has used her phone in a month?

For her phone service Mai pays a monthly fee of 19 and she pays an additional 004 per minute of use The least she has been charged in a month is7028 What are th class=

Respuesta :

We have a phone service fee which can be divided in:

- A fixed fee of $19 per month.

- A variable fee of $0.04 per minute, so that the cost for m minutes is 0.04*m.

We can add the two fees to express the total cost in function of the minutes as:

[tex]C(m)=19+0.04m[/tex]

For a month where the cost is C(m) = 70.28, we can calculate the minutes as:

[tex]\begin{gathered} C(m)=70.28 \\ 19+0.04m=70.28 \\ 0.04m=70.28-19 \\ 0.04m=51.28 \\ m=\frac{51.28}{0.04} \\ m=1282 \end{gathered}[/tex]

Answer: if she pays at least $70.28, she has talked at least m = 1282 minutes per month.

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