Question

Difficulty: MediumSystems of Linear Inequalities in Two Variables

An artist creates custom oil paintings and charcoal sketches.

* Each oil painting, xx, requires 44 hours of setup time and 22 hours of finishing time.
* Each charcoal sketch, yy, requires 11 hour of setup time and 33 hours of finishing time.

Each week, the artist can spend at most 2020 hours on setup time and at most 3030 hours on finishing time. Which of the following systems of inequalities represents this situation?

  1. A
    4x+y202x+3y30\begin{aligned} 4x + y &\ge 20 \\ 2x + 3y &\ge 30 \end{aligned}
  2. B
    4x+2y20x+3y30\begin{aligned} 4x + 2y &\le 20 \\ x + 3y &\le 30 \end{aligned}
  3. 4x+y202x+3y30\begin{aligned} 4x + y &\le 20 \\ 2x + 3y &\le 30 \end{aligned}Answer
  4. D
    4x+y302x+3y20\begin{aligned} 4x + y &\le 30 \\ 2x + 3y &\le 20 \end{aligned}

Answer

The system of inequalities consisting of the inequalities 4x+y204x + y \le 20 and 2x+3y302x + 3y \le 30
The variable xx represents the number of oil paintings and yy represents the number of charcoal sketches. Setup time constraint: each oil painting requires 44 hours and each charcoal sketch requires 11 hour. Thus, the total setup time is 4x+y4x + y hours. Since the artist can spend at most 2020 hours on setup time, this is represented by the inequality 4x+y204x + y \le 20. Finishing time constraint: each oil painting requires 22 hours and each charcoal sketch requires 33 hours. Thus, the total finishing time is 2x+3y2x + 3y hours. Since the artist can spend at most 3030 hours on finishing time, this is represented by the inequality 2x+3y302x + 3y \le 30. Combining these gives the correct system.

Step-by-Step Solution

1
Identify the variables and setup times for each type of artwork to write the setup time inequality.
The total setup time is 4x+y4x + y hours. Since the limit is at most 2020 hours, the inequality is 4x+y204x + y \le 20.
To establish the mathematical representation of the setup time constraint.
2
Identify the variables and finishing times for each type of artwork to write the finishing time inequality.
The total finishing time is 2x+3y2x + 3y hours. Since the limit is at most 3030 hours, the inequality is 2x+3y302x + 3y \le 30.
To establish the mathematical representation of the finishing time constraint.
3
Combine the two inequalities into a system.
The system of inequalities is 4x+y204x + y \le 20 and 2x+3y302x + 3y \le 30.
To find the system that represents both constraints simultaneously.

Key Concept

Translating real-world constraints into a system of linear inequalities in two variables.
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