# Lesson: Inverse Operations

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### Lesson Objective

SWBAT check accuracy of a problem by using the inverse operation.

### Lesson Plan

Materials Needed: DN Worksheet, white board, dry erase markers, Inverse Graphic Organizer for guided practice, and IND Worksheet.
Vocabulary: multiplication, array, model, group, counting, product, multiple

……….
Do Now (3 -5 min): Teacher hands a DN Worksheet to every student and asks the students to complete the worksheet independently. (fact families + / - )

Opening (2 -3 min): Teacher quickly reviews answers to the Do Now and then says, “Today, we are going to continue learn about the relationship between multiplication and division. By the end of this lesson, you will be able to check accuracy of a problem by using the inverse operation.”

Direct Instruction (10 min): The teacher begins, “We have been working on multiplication for several days. Tomorrow we are going to begin division, so today we are going to learn about how multiplication and division is related. In the math world, they are called inverse operations. Who knows the opposite of addition? [Subtraction]. Exactly! Well, division is the opposite of multiplication. Today we are going to see the relationship using fact families. We practiced addition and subtraction fact families in our Do Now. Watch as I show you a multiplication and division fact family.

8 x 3 = 24
3 x 8 = 24
24 ÷ 3 = 8
24 ÷ 8 = 3

The teacher should walk through each number sentence and explain the relationship. For example, “8 x 3 = 24, well I know that 3 x 8 = the same thing, so 3 x 8 = 24. If division is the opposite of multiplication, I need to take the product and divide it by each multiplier. That means 24 ÷ 3 = 8 and 24 ÷ 8 = 3” The teacher should then draw these into a fact triangle.

The teacher should then walk through another example, before going to guided practice.

6 x 5 = 30
5 x 6 = 30
30 ÷ 5 = 6
30 ÷ 6 = 5

Guided Practice (10 min): The teacher should then pass out the Inverse Graphic Organizer and explain to the students that they will now be working on making their own fact triangles. The teacher should then put the following facts on the board/chart and walk around to assist the students.

5 x 4 = 20
3 x 7 = 21
8 x 4 = 32
6 x 6 = ?
4 x 7 = ?
5 x 3 = ?

Independent Practice (10 min): Each student is given the IND Worksheet and asked to complete it individually and turn it in.

Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to ask what they learned about.

### Lesson Resources

 Multiplication Inverse GO   Classwork 2 IND fact families   Classwork 1 DN_Lesson 4_fact_families.pdf 4