Question

A plumber charges an initial amount to make a house call plus an hourly rate for the time he is working. A 1-hour job costs $90 and a 3-hour job $210. What is the initial amount and the hourly rate that the plumber charges

Answer 1

Answer:the initial amount is $30

The hourly rate is $60

Explanation:

Let x represent the fixed cost or the initial amount to make a house call.

Let y represent the amount that the plumber charges per hour.

A 1-hour job costs $90. It means that

x + y = 90

x = 90 - y- - - - - - - - - - 1

A 3-hour job cost $210. This means that

x + 3y = 210 - - - - - - - - - - - - -2

Substituting equation 1 into equation 2, it becomes

90 - y + 3y = 210

90 + 2y = 210

2y = 210 - 90 = 120

y = 120/2 = 60

Substituting y = 60 into equation 1, it becomes

x = 90 - 60 = 30