## Addend Pairs to 12

Students practice their addition facts for sums up to 12 by playing a game. They add to their personal addition charts. Students are encouraged to practice the facts that they have not yet mastered. Finally, triangular flash cards help students practice addition facts.

Put students in pairs, and provide them with two number cubes and a game board for Cover Up.

Cover Up |

- Each student chooses a section of the game board.
- When it is your turn, roll the two number cubes and find the sum of the two numbers that come up.
- Cover up the number on your part of the board for that sum, if it's not yet covered up.
- Then, it's the other player's turn.
- The first students to cover up all 11 numbers is the winner.
- When one student wins, the pair should remove all the counters and play again.

After the class has played for several minutes, ask them to return to their seats and take out their personal addition charts. Ask them to add any addition facts of which they are sure to the chart.

Continue the lesson by having each student review his or her copy of the Facts I Know Activity Sheet, adding known facts as necessary. Then display a large copy of an addition chart on the board or overhead. Call on volunteers to come to the front and circle one fact that they have studied so far.

When the students have circled all the facts that they have studied, direct their attention to the facts that are left:

4 + 9

5 + 8, 5 + 9

6 + 7, 6 + 8, 6 + 9

7 + 6, 7 + 8, 7 + 9

8 + 5, 8 + 6, 8 + 7, 8 + 9

9 + 4, 9 + 5, 9 + 6, 9 + 7, and 9 + 8

Ask the class what they know that will help them learn fewer than 18 facts. Encourage them to remember the commutative property.

Remind the students that some of these facts belong to the doubles-plus-one group. Ask them to identify them. [These facts are 6 + 7, 7 + 8, and 8 + 9.] Now circle in another color the remaining six facts: 4 + 9, 5 + 8, 5 + 9, 6 + 8, 6 + 9, and 7 + 9.

Place the students in pairs and assign each student three addition facts from the following: 4 + 9, 5 + 8, 5 + 9, 6 + 8, 6 + 9, 7 + 9, as a set of demonstration facts. Have the students cut two triangular shapes from each of three index cards. Demonstrate how to make a triangular flash card by putting the two addends in two of the corners and the sum in the other corner, as in the example below.

Now ask the students to make triangular fact cards for the facts they choose, then trade the cards with their partner. Ask each student to cover the sum on one card with his or her thumb, show the card to the other student, and ask him or her to tell the sum.

Conclude the lesson by asking students to be sure that they have covered both facts in a commutative pair [For example, 6 + 7 and 7 + 6]. Finally, ask them to choose two facts and make triangular flash cards for them. Encourage the students to take those two new cards and the three they made in this lesson home to practice.

- Counters
- Number cubes
- Paper
- Markers
- Index cards
- Scissors
- Cover Up Activity Sheet
- Facts I Know Activity Sheet

**Assessments**

- The students will vary in how quickly they attain command of the addition facts at the immediate-recall level. Therefore, you may find your entries in the Class Notes recording sheet especially helpful in grouping students for remedial instruction. This information may also be helpful in deciding on appropriate homework assignments.

**Questions for Students**

1. What sums can you get when you roll two number cubes? How can you get three as a sum? How can you get eleven as a sum? Seven as a sum? Eight as a sum?

[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12; 1+2; 5+6; 1+6, 2+5; 2+6, 3+5, 4+4.]

2. What happens when one addend is one? When one addend is zero? How can knowing this help you learn the addition facts

[The sum is one more than the other addend; The sum is the other addend.]

3. What doubles can you get with number cubes?

[2, 4, 6, 8, 10, 12.]

4. What pairs of numbers have a sum of 12? 18? Are any of these pairs doubles? What other doubles have you studied?

[0+12, 1+11, 2+10, 3+9, 4+8, 5+7, 6+6; 0+18, 1+17, 2+16, 3+15, 4+14, 5+13, 6+12, 7+11; 8+10, 9+9; Yes, 6+6 and 9+9 are doubles.]

5. What pairs of numbers have a sum of 13? Of 15? Of 17

[0+13, 1+12, 2+11, 3+10, 4+9, 5+8, 6+7; 0+15, 1+14, 2+13, 3+12, 4+11, 5+10, 6+9; 7+8; 0+17, 1+16, 2+15, 3+14, 4+13, 5+12, 6+11, 7+10, 8+9.]

**Teacher Reflection**

- Which students have only a few addition facts learned? What activities should I plan for them?
- What extension activities are appropriate for the students who have learned all their addition facts?
- What adjustments will I make the next time that I teach this lesson?
- Which students are able to identify the facts they have learned? How can others be helped to achieve this goal?
- Which students have only a few addition facts left to learn? What activities should I plan for them?

### Finding Addition Patterns

### Finding Sums to Six

### Some Special Sums

### Wrapping up the Unit

### Learning Objectives

Students will:

- Practice addition facts up to 12
- Create a learning tool for memorizing the rest of the addition facts

### NCTM Standards and Expectations

- Develop and use strategies for whole-number computations, with a focus on addition and subtraction.

- Develop fluency with basic number combinations for addition and subtraction.

### Common Core State Standards – Mathematics

-Kindergarten, Algebraic Thinking

- CCSS.Math.Content.K.OA.A.5

Fluently add and subtract within 5.

Grade 1, Algebraic Thinking

- CCSS.Math.Content.1.OA.B.4

Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.

Grade 1, Algebraic Thinking

- CCSS.Math.Content.1.OA.C.6

Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

Grade 1, Number & Operations

- CCSS.Math.Content.1.NBT.C.4

Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.

Grade 2, Algebraic Thinking

- CCSS.Math.Content.2.OA.B.2

Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.

Grade 2, Number & Operations

- CCSS.Math.Content.2.NBT.B.5

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

Grade 2, Number & Operations

- CCSS.Math.Content.2.NBT.B.6

Add up to four two-digit numbers using strategies based on place value and properties of operations.

Grade 2, Number & Operations

- CCSS.Math.Content.2.NBT.B.7

Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

Grade 2, Number & Operations

- CCSS.Math.Content.2.NBT.B.9

Explain why addition and subtraction strategies work, using place value and the properties of operations.

### Common Core State Standards – Practice

- CCSS.Math.Practice.MP6

Attend to precision.