Question

For her phone service, Amy pays a monthly fee of $18 , and she pays an additional $0.07 per minute of use. The least she has been charged in a month is 121.25. What are the possible numbers of minutes she has used her phone in a month? Use m for the number of minutes, and solve your inequality for m

Answer 1

The total fee has two parts:

0. A monthly fee of $18, that does not depends on the minutes of use.

,

1. A variable fee of 0.07*m, where m are the minutes of use.

Then, we can express the fee C(m) as:

`C(m)=18+0.07m`

The least she has been charged is $121.25.

Then, we can express this as C(m) ≥ 121.25.

We can find the number of minutes m as:

`\begin{gathered} C(m)\ge121.25 \\ 18+0.07m\ge121.25 \\ 0.07m\ge121.25-18 \\ 0.07m\ge103.25 \\ m\ge(103.25)/(0.07) \\ m\ge1475 \end{gathered}`

Answer: she has used the phone at least for 1475 minutes.