 Help your children learn about inverse relationships between addition and subtraction with this worksheet. The questions get progressively more difficult. The purpose of this unit of three lessons is to develop an understanding of how the operations of addition and subtraction behave and how they relate to one. In Grade 1, students extend their prior work with small numbers to begin developing build their understanding of the relationship between addition and subtraction. The lesson plan(s) have been written with specific standards in mind.

Write and read sets of related addition and subtraction equations. Explain, in their own words, the inverse relationship between addition and subtraction. It is not necessary for students to know the name for this. Activity 1 Begin by reading together the concluding notes from Session 1. Distribute sets of Family Shuffle cards Attachment 1 to students. To recognise related addition and subtraction equations Explain how to play. Each student has one set of 16 shuffled cards.

These are dealt out, face up, in a four-by-four array. Two cards any are removed from the array and set aside, creating two empty spaces in the array. The two cards that were set aside are replaced to complete the array.

Students could write their own sets to create alternative puzzles. Ask students what they notice about what is happening with the numbers. Read to the class or have written on the class chart this scenario. Discuss what is happening in these equations.

Record several of these in words and in equations on the class chart. Read to the class or have written on the class chart this scenario or a similar one relevant for the class. Once again, discuss what is happening in these equations. Explain that we say this relationship between addition and subtraction, is known as an inverse relationship. Record this in answer the question posed in Step 2 above. Have students suggest a meaning for inverse, then confirm this with a dictionary.

Make paper, pencils and felt pens available to the students. Session 3 Recognise that addition is commutative but that subtraction is not. Recognise how knowing about number families is helpful for solving problems. Solve number problems that involve application of the additive inverse.

## Gr. 1 Unit: Add & and Subtract within 20

Activity 1 Begin by sharing the student work from Session 2, Activity 2, Step 6. In particular highlight the commutative property of addition. Also highlight the related subtraction facts. Distribute the addition and subtraction grids Attachment 2 to each student. Use the larger class copies to model how to complete each grid.

Highlight the importance of the students writing their observations about each grid once they are completed. These observations should include number patterns and the fact that the subtraction grid cannot be fully completed. Once completed, have students share what they notice and record their observations.

### Inverse Relationship of Addition Subtraction Using Calculator Game - Addition Game | Turtle Diary

On the class addition grid look for the same sums for both addends. Discuss the pattern and also notice the pattern of doubles Write this statement on the class chart and read it with the students: We can carry out addition of two numbers in any order and this does not affect the result. Introduce the word commutative. Record a student statement that states, in their words, that addition is commutative, subtraction is not. Activity 2 Have students complete the number problems on Attachment 3. In giving instructions highlight the importance of the students recording equations and on explaining what is happening with the numbers in the problems. Have students share their work. Discussion should focus on highlighting the relationships between addition and subtraction.

Activity 3 Introduce the game Families on Board. Model how it is played. The game is played in pairs. These models also help to develop strategies to solve arithmetic problems which involve these operations. Students understand connections between counting and addition and subtraction e.

• Math Fact: Relationship Between Addition & Subtraction
• Number families and relationships
• Inverse Relationship of Addition Subtraction Using Calculator Game - Addition Game

They use properties of addition to add whole numbers and to invent and use increasingly sophisticated strategies based on these properties e.

By developing, discussing, and comparing a variety of solution strategies, children build their understanding of the relationship between addition and subtraction. Why do I need mathematical operations?

How do I know which mathematical operation to use? What are different ways to count? What are the most efficient ways to count? In what ways can numbers be composed and decomposed? A question is essential when it stimulates multi-layered inquiry, provokes deep thought and lively discussion, requires students to consider alternatives and justify their reasoning, encourges re-thinking of big ideas, makes meaningful connections with prior learning, and provides students with opportunities to apply problem-solving skills to authentic situations.

Available Model Lesson Plans The lesson plan s have been written with specific standards in mind.