Question

A plumber charges $75 for the first 30 minutes of each house call plus $2 for each additional minute that she works. The plumber charges Adam $113 for her time. For what amount of time, in minutes, did the plumber work?

Answer 1

49 minutes

Explanation:

We can construct a formula for the plumber's fee.

`C = color(red)(75) + color(blue)(2n)`

The red 75 denotes the $75 that is charged for the first half hour. `n` is the number of minutes over that that she works.

Cost is $113 so

`113 = 75 + 2n`

Can subtract 75 from both sides of the equation without changing anything about it:

`113-75 = 38 = 2n`

Divide both sides by 2:

`19 = n`

She worked 19 minutes over the first 30, so worked `19+30 = 49` minutes in total.