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4.5 Graphing a System of Inequalities

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Last updated about 1 year ago
26 questions
Note from the author:
OBJECTIVES & STANDARDS
Math Objectives
  • Graph systems of linear inequalities
  • State solutions to the system using the solution region on the graph
  • Understand special cases of systems of linear inequalities
Common Core Math Standards
  • Link to all CCSS Math
  • CCSS.PRACTICE.MP1
  • CCSS.HSA.REI.D.12
  • CCSS.HSF.LE.B.5
Personal Finance Objectives
  • Work with a budget given restraints
National Standards for Personal Financial Education
Spending
  • 1b: Develop a budget to allocate current income to necessary and desired spending, including estimates for both fixed and variable expenses.
DISTRIBUTION & PLANNING
Distribute to students
  • Student Activity Packet
  • Application Problems
OBJECTIVES & STANDARDS
Math Objectives
  • Graph systems of linear inequalities
  • State solutions to the system using the solution region on the graph
  • Understand special cases of systems of linear inequalities
Common Core Math Standards
  • Link to all CCSS Math
  • CCSS.PRACTICE.MP1
  • CCSS.HSA.REI.D.12
  • CCSS.HSF.LE.B.5
Personal Finance Objectives
  • Work with a budget given restraints
National Standards for Personal Financial Education
Spending
  • 1b: Develop a budget to allocate current income to necessary and desired spending, including estimates for both fixed and variable expenses.
DISTRIBUTION & PLANNING
Distribute to students
  • Student Activity Packet
  • Application Problems
Intro-Warm-Up
Learn It
Practice It
Practice It
Apply It
Level 3: Bonus
0
0
INTRO: How Many Hours Should Ben Work?
Read the scenario below and use it to answer the questions.
Ben is working two jobs: Delivering pizzas at $12 an hour and working at a grocery store making $15 an hour. Between the two jobs, he can work a maximum of 20 hours per week and needs to make at least $250 to cover his expenses.
2
Question 1
1.
State two different combinations of hours that Ben can work at each job to meet all of the criteria of this situation._______ _______
1
Question 2
2.

Can you think of a way to summarize ALL possible solutions without having to make a list?

What is a System of Inequalities?
As you can see from the Intro question, there are some situations that have multiple different answers and it can be challenging to summarize ALL of them using words.  Systems of Inequalities give us the ability to summarize all of the possible solutions using a graph!
A system of linear inequalities is a set of two or more linear inequalities that are graphed on the same coordinate plane.
The solution of a system of linear inequalities is the region of the graph where all shaded regions overlap.  All points in the region make both inequalities true.

Review the example problem to solve the following system of linear inequalities by graphing.
y > -2x + 4
y < x - 2

1. Graph the first inequality
Graph the border line, determine dashed (< or >) or solid line (< or >), then use a test point to determine the solution region.


2. Graph the second inequality
Graph the border line, determine dashed (< or >) or solid line (< or >), then use a test point to determine the solution region.


3. Find overlap
Find the area of the graph that is shaded in for both inequalities.


4. Identify solutions.
Solutions are points that fall in the shaded region for BOTH inequalities. Remember points on dashed lines are NOT solutions but points on solid lines ARE solutions.
Some example solutions:
(4, 0)
(6, 2)
(7, -1)
(8, 4)
3
3
3
3
For each system of inequalities, graph to show the solution region and state one solution to the system.
1
Question 7
7.

For each system of inequalities, graph to show the solution region and state one solution to the system.

1
Question 8
8.

For each system of inequalities, graph to show the solution region and state one solution to the system.

1
1
Systems of Inequalities Applications
Let’s revisit Ben from the Intro. Here’s the scenario again:
Ben is working two jobs: delivering pizzas at $12 an hour and working at a grocery store making $15 an hour. Between the two jobs, he can work a maximum of 20 hours per week and needs to make at least $250 to cover his expenses.
1
Question 11
11.
Write two inequalities that represent Ben’s situation where x is the number of hours worked delivering pizzas and y is the number of hours worked at the grocery store._______ _______
1
1
Question 13
13.
Using your graph, state 4 points that are in the overlapping solution region and what they mean to Ben._______ _______ _______ _______
1
1
1
APPLICATION: Graphing a System of Budget Inequalities

Level 1

Budgeting for the Big Show
Your high school theater department is setting their budget for their annual spring musical. They know that their theater can hold a maximum of 1,300 people for the show. They plan to sell tickets for $9 in advance and $12 on the day of the show. They know that they must make at least $12,500 to cover the costs of their budgeted expenses.
1
Question 17
17.
Write a system of linear inequalities that represents this situation. Let x represent the number of tickets sold in advance and y represent the number of tickets sold on the day of the show._______ _______
1
Question 18
18.

Graph the system of inequalities on the coordinate plane.

1
Question 19
19.
State 3 points that are in the solution space and what they mean in the context of the theater department’s budgeting situation._______ _______ _______
2
Sammi is organizing an end of summer barbeque. She needs to make at least 50 sandwiches and has a budget of $30. She goes to the grocery store to get buns. The grocery store sells hamburger buns in packages of 8 and hotdog buns in packages of 6.
The following system of equations represents Sammi’s barbecue planning:
8x + 6y > 50
3.5x + 2.25y < 30
2
Question 21
21.
What does each variable represent about the barbeque?
x=_______
y=_______
1
Question 22
22.

What does the second inequality tell us about the situation?

1
1
Question 24
24.

State 3 solutions and what they mean in the context of Sammi’s barbecue.

Question 25
25.

Write a system of linear inequalities that has the point (4, 7) as a solution. At least one of your equations should have a slope not equal to zero.

Question 26
26.

Write a word problem that tells a story about your system of inequalities. Be sure to:
  • Describe all parts of the story that contribute to your equations
  • Define all variables
  • Create a graph that shows that (4, 7) is a solution

Question 3
3.
Solve the system of linear inequalities by graphing in Desmos. Then, state two solutions.
_______ _______
Question 4
4.
Solve the system of linear inequalities by graphing. Then, state two solutions._______ _______
Question 5
5.
Solve the system of linear inequalities by graphing. Then, state two solutions._______ _______
Question 6
6.
Solve the system of linear inequalities by graphing. Then, state two solutions._______ _______
Question 9
9.

For each system of inequalities, graph to show the solution region and state one solution to the system.

Question 10
10.

For each system of inequalities, graph to show the solution region and state one solution to the system.

Question 12
12.

Use this Desmos Graph to enter your equations and view the solution region. Tip: To enter < in Desmos, just type <=

(screen shot your answer into the drawing)

Question 14
14.

If Ben’s expenses changed to at least $1000 instead of $250, how would your equations change? Make those changes in Desmos. (You will need to zoom out to see both graphs)


*screen shot the graphs in the drawing*

Question 15
15.
State a point that falls in the new solution region._______
Question 16
16.

What does your answer to question 5 mean about Ben covering $1000 in expenses in a week?

Question 20
20.
State 1 point that is a solution to one of the inequalities but not the other._______
What does this point represent in the theater department’s budgeting situation?_______
Question 23
23.

Graph the system of inequalities using the grid below