New homeowners hire a painter to paint rooms in their house. The painter pays $60 for supplies and charges the homeowners $20 for each room they want painted.

Which of the following graphs shows the relationship between the amount of money the painter earns, in dollars, and the number of rooms he paints?
a coordinate grid with the x axis labeled rooms painted and the y axis labeled amount of money earned and a line going from the point 0 comma 60 through the point 3 comma 0
a coordinate grid with the x axis labeled rooms painted and the y axis labeled amount of money earned and a line going from the point 0 comma 60 through the point 3 comma 120
a coordinate grid with the x axis labeled rooms painted and the y axis labeled amount of money earned and a line going from the point 0 comma negative 60 through the point 3 comma 0
a coordinate grid with the x axis labeled rooms painted and the y axis labeled amount of money earned and a line going from the point 0 comma negative 60 through the point 3 comma negative 120

1 answer

To determine the relationship between the amount of money the painter earns and the number of rooms painted, let's break down the problem:

  1. The painter spends $60 on supplies. This means that the initial (fixed) cost the painter incurs before earning any money is $60.

  2. The painter charges $20 for each room painted. Therefore, if the painter paints \( x \) rooms, the amount earned from painting can be calculated as \( 20x \).

  3. The total amount earned (which is the revenue from painting minus the initial cost) can be expressed as: \[ \text{Total Earnings} = 20x - 60 \] Here, \(20x\) is the income from painting \( x \) rooms, and we subtract the $60 cost for supplies.

  4. The formula \( 20x - 60 \) indicates that when \( x = 0 \) (no rooms painted), the painter's earnings are \(-60\). This is where the line starts on the y-axis.

  5. As \( x \) increases (more rooms painted), the earnings will increase by $20 for each additional room.

By plotting this equation, we see:

  • The graph starts from the point \( (0, -60) \) since the painter incurs a fixed cost of $60 before earning anything.
  • When the painter paints 3 rooms, the earnings will be: \[ 20 \times 3 - 60 = 60 - 60 = 0 \]

So the painter earns $0 after painting 3 rooms.

Given this analysis, the correct graph representation would be the one that starts at \( (0, -60) \) and passes through \( (3, 0) \):

The correct answer is: a coordinate grid with the x axis labeled rooms painted and the y axis labeled amount of money earned and a line going from the point 0 comma negative 60 through the point 3 comma 0.