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In this activity, students critique a statement or response that is intentionally incorrect (MP3). The example given represents a common mistake made by students and prompts students to consider the meaning and placement of inequality symbols in relation to a number line.
Give students 2–3 minutes of quiet work time, and follow with a whole-class discussion.
Andre drew this number line to represent .
Do you agree with Andre’s number line? Explain your reasoning.
The purpose of this discussion is to address a common mistake made by students when graphing or interpreting an inequality where the variable is on the right side of the inequality. Begin by inviting 2–3 students to share their responses and reasoning. If not mentioned by students, discuss the following questions:
In this activity, students interpret inequalities that represent constraints or conditions in a real-world situation. They find solutions to an inequality and reason about the context’s limitations on solutions (MP2).
Give students 10 minutes of quiet work time, and follow with a whole-class discussion.
Noah scored points in a basketball game.
Draw two number lines to represent the solutions to the two inequalities.
Name a possible value for that is a solution to both inequalities.
Name a possible value for that is a solution to but not a solution to .
The goal of this discussion is to extend the context of scored points in a basketball game by considering additional situations. Invite students to share their responses to each question. If necessary, have a student share what they know about how scoring works in basketball (free throws are worth 1 point, regular baskets are worth 2 points, baskets shot from outside a certain line are worth 3 points). Then discuss the following questions:
In this activity, students describe unbalanced hanger diagrams with inequalities. Students construct viable arguments and critique the reasoning of others during partner and whole-class discussions about how unknown values relate to each other (MP3).
Display this diagram of an unbalanced hanger:
Discuss the following questions:
Arrange students in groups of 2. Give students 5 minutes of quiet work time, followed by 2 minutes for a partner discussion. Tell students to discuss their thinking with their partners and that if there are disagreements, work to reach an agreement. Follow with a whole-class discussion.
Here is a diagram of an unbalanced hanger.
Let be the weight of one pentagon and be the weight of one square. Write an inequality to represent the relationship of the 2 weights.
If the pentagon weighs 8 ounces, write another inequality to describe the situation. What does this inequality mean for this situation?
Graph the solutions to this inequality on the number line.
Here is another diagram of an unbalanced hanger.
Andre writes the following inequality, where represents the weight of one circle: . Do you agree with his inequality? Explain your reasoning.
The purpose of the discussion is for students to explain how they used inequalities to compare the weights of different shapes on the hanger diagrams. Invite groups share their responses to the questions. If time allows, ask students to describe any disagreements or difficulties they had and how they resolved them.
Remind students that a circle weights 12 ounces and a pentagon weighs 8 ounces and display these two diagrams for all to see:
Ask students:
The purpose of this discussion is for students to practice writing inequalities to represent real world situations involving public health or safety. Begin by asking students to think of situations where limits or ranges of values can be important to public health or safety. Some examples include weight limitations on an elevator, safe dosages for medication, tire pressure, speed limit, and temperatures for growing carrots.
Then ask students to define variables and write inequalities to represent these situations. Select 2 or 3 students to share their responses. Record and display those responses for all to see, using the appropriate symbols. Here are some questions to consider during discussion:
An inequality that describes a real-world situation may have number solutions that make the inequality true, but those solutions may not always make sense in real life.
For example:
A basketball player scored more than 11 points in a game. This can be represented by the inequality , where is the number of points scored. Numbers such as 12, , and 130.25 are all solutions to the inequality because they each make the inequality true.
In a basketball game, however, it is only possible to score a whole number of points, so fractional and decimal scores are not possible. It is also highly unlikely that one person would score more than 130 points in a single game.
This particular situation limits the solutions.
Here is another example:
It rained for less than 30 minutes yesterday (but it did rain). This can be represented by the inequality , where represents the number of minutes of rain yesterday. Even though numbers such as 18.2, and -7 are all less than 30, our solutions are limited to positive numbers since 0 or a negative number of minutes would not make sense in this context.
To show the upper and lower boundaries, we can write two inequalities:
Inequalities can also represent a comparison of two unknown numbers.