Question

How many minutes can you talk if you use a $5 phone card to call a friend and the call is $.50 for the first minute and $.15 for each additional minute (or part of a minute)?

Answer 1

You can talk for `30` minutes.

Explanation:

First, let's list out what we know:

We have a `$5` phone card.

The first call is `$0.50`.

Every minute after that is `$0.15`.

Now, let's let `m` be the number of minutes you can talk.

We know that the minutes times the dollar amount must equal to `5`, and that `$0.50` is a constant (no matter how many minutes you call `$0.50` is still there.

Since we don't know how many minutes there are but we know the cost for every minute after, that becomes `0.15m`.

Set the equation:
`0.50 + 0.15m = 5`

Now solve for `m`. Subtract `color(blue)(0.50)` from both sides of the equation:
`0.50 + 0.15m quadcolor(blue)(-quad0.50) = 5 quadcolor(blue)(-quad0.50)`

`0.15m = 4.5`

Then divide both sides by `color(blue)0.15`:
`(0.15m)/color(blue)0.15 = 4.5/color(blue)0.15`

Therefore,
`m = 30`.

You can talk for `30` minutes.

Hope this helps!