Lesson: Inequalities: Set Up with Variables
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Lesson Objective
SWBAT set up inequalities with variables (letters or pictures)
Lesson Plan
Materials Needed: DN Worksheet (cut in half), white board, dry erase markers, IND worksheet (double sided)
Vocabulary: greater than, less than, equal to, operations, inequalities, variables, signal words
……….
Do Now (3 5 min): Each student is handed half of the worksheet and asked to complete it independently. The worksheet reviews inequalities with addition, subtraction, multiplication, and division.
Opening (3 5 min): Teacher quickly reviews answers to the Do Now and then says, “Yesterday, we learned about using variables in division word problems. In this unit, we have learned about inequalities and using variables in addition, subtraction, multiplication, and division word problems. Today we are going to work on understanding the properties of inequalities. We won’t be working with numbers, only variables. By the end of this lesson, you will all be able to set up inequalities with variables. Are there any questions?”
Direct Instruction (10 – 12 min): Teacher then writes the following inequality on the board M > S, and asks “What in the world does that mean? Does anyone have any clue? I am confused since there are no numbers in that inequality, or number sentence. [The quantity of M is bigger than the quantity of S]. Now, while that is the correct answer. This inequality still doesn’t mean much to me, unless I understand what S and M represent. Watch as I show you how to set up an inequality with variables from a word problem. For this problem I will identify the variables within the problem.”
Example 1: Allie and Kenny wrote a number sentence to show that Allie got a higher score than Kenny on their math test. In their number sentence,
• A represents Allie’s score and
• K represents Kenny’s score.
What should the number sentence look like?
Step 1: Read the word problem
Step 2: Select/Identify variables A and K
Step 3: Set up inequality A > K
Step 4: Check Allie’s score is greater than Kenny’s
Teacher then continues, “Remember that the inequality sign is like an alligator’s mouth and always opens toward the bigger number. In this case, Allie’s math score is bigger so the inequality sign points to A which is representing Allie’s score. Now let’s try one that does not identify the variables for us.”
Example 2: Tina bet her friend Deena that she could eat more gummy bears that her in 5 minutes. Deena ate 10 times the amount that Tina ate.
What should the number sentence look like to represent the winner of the bet?
Step 1: Read the word problem
Step 2: Select/Identify variables T and D
Step 3: Set up inequality D > T
Step 4: Check Deena ate more gummy bears that Tina
Teacher continues, “Ok, what were the variables in the last problem based on? [student’s names] Very good! So w, did everyone see how I did that? Who can tell me what the variables should be? [Tand D].” Teacher continues setting up the inequality explaining steps as she writes them on the board.
Guided Practice (10 min): Teacher then completes Example 3 for guided practice. An additional problem can be added if students are having difficulty.
Example 3: In Mr. Vince’s science class the students are comparing the nutritional information of candy bars. Today they compared Snickers and Twix bars. Snickers has 280 calories and Twix has 280? Write a number sentence or inequality that compares the calories in these two candy bars.
Step 1: Read the word problem
Step 2: Select/Identify variables S and T
Step 3: Set up inequality S = T
Step 4: Check Snickers and Twix have the same # of calories
Example 4: In Mr. Vince’s science class the students are comparing the nutritional information of candy. Today they compared Skittles and Starburst. Skittles had more grams of sugar than Starburst. Write a number sentence or inequality that compares the grams of sugar in these two candies.
Step 1: Read the word problem
Step 2: Select/Identify variables Sk and St
Step 3: Set up inequality St < Sk
Step 4: Check Starburst has less sugar than Skittles
Independent Practice (10 min): Teacher gives each student their own copy of the Independent Practice (IND) worksheet. Teacher circulates the room to answer individual student’s questions.
Closing (23 min): Teacher calls the attention of the students back toward the front of the class to quickly review the answers to the Independent Practice worksheet/ ask what we learned about.
Lesson Resources
IND Lesson 7 Set Up Inequality Classwork  
DN Lesson 7 
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