# Lesson: Finding a NEW Total Cost

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### Lesson Objective

SWBAT solve for total cost after solving for the unit cost

### Lesson Plan

Materials Needed: DN worksheet, GP worksheet, IND practice worksheet
Vocabulary: unit, cost, multiplication, division, total

……….
Do Now (2 - 3 min): Teacher gives each student a copy of their DN Worksheet and asks them to complete the work quietly.

Opening (2 -3 min): Teacher reviews the DN Worksheet. Teacher says, “For the past two days we have been discussing unit cost and total cost. You have learned that you multiply when you have the unit cost and you want to know the total cost. You know that you divide if you have the total cost and you want to know the unit cost. Today, we are going to put our knowledge to the test and try to solve two-step word problems. By the end of the lesson, you will be able to solve for the total cost after solving for the unit cost.

Direct Instruction (10 - 12 min): Teacher writes the following on the board:

A total cost of five shirts \$25, how much does each shirt cost? What is the total cost of 10 shirts?

Teacher says, “Lets begin by finding the unit cost of a shirt. You have the total cost of the shirts and you want to know the unit cost, so what operation are you going to use? [Division] Very good, we want to divide the total cost by the amount of units. What is the total cost? [\$25] Excellent, and how many units do we have?  Great! So if I divide 25 by 5, what is the answer?  Awesome, so the unit cost of each shirt is \$5.

Now, believe it or not, you have just completed the first step of the two-step process we are learning about today. In all of the problems we see today, you want to find the unit cost of the item first. The second step comes in if I were to ask you how much it would cost to buy 10 shirts. What do I need to do to find the cost of 10 shirts now that I know the cost of one shirt? [Multiply 10 by \$5] You all are awesome! I want to multiply the cost of one shirt by the amount of shirts I want to buy, in this case that is 5 x 10. What is 5 x 10?  Great, so the cost of 10 shirts would be \$50.”

Teacher writes the following on the board:

Step 1: Find the unit cost of the item
Step 2: Multiply the unit cost by the number of items to find the total cost

Teacher continues, “If you use these two steps, you will not have any trouble with these word problems. Remember, like I said earlier, you are just combining two skills that you already know. Lets break into groups and solve three two-step problems; then we will review these problems together before I have you practice on your own. Remember to follow the two steps!”

Guided Practice (10 -12 min): Teacher gives each math group a GP worksheet and circulates the room to answer any questions. When most students are finished, the teacher reviews the answers to each problem on the board, making sure to highlight the importance of following both steps in the process.

Independent Practice (10 min): The teacher hands out the IND Practice worksheet. Students are asked to complete the worksheet independently and turn it in.

Closing (2-3 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   Classwork DN lesson 7 unit cost   Starter / Do Now
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