Question

A cell phone carrier charges a fixed monthly fee plus a constant rate for each minute used. Part 1. In January, the total cost for 300 minutes was $ 68 while in February, the total cost for 275 minutes was $ 66.5 . The constant charge for each minute used is:

Answer 1

The constant charge for each minute used is $50

Explanation:

In order to solve this problem we will need to set two variables up. In this case:

F = constant Fee

R = rate per minute used

So the cost for the month of January is calculated like this:

F+300R=68

and the cost for February is calculated like this:

F+275R=66.5

So no we have a system of equations we can solve simultaneously. This can be solved by using different methods, elimination, substitution, graphically or by using matrices. I will solve this by substitution.

So let's solve the first equation for R:

`R=(68-F)/(300)`

and let's substitute this first equation into the second equation:

`F+275((68-F)/(300))=66.5`

and now we can solve this for F:

`F+11((68-F)/(12))=66.5`

We can multiply both sides by 12 so we get:

12F+11(68-F)=798

12F+748-11F=798

F= $50