# Lesson 18: Addition within 20

## Lesson Objectives

- Review Touching/Counting Patterns for numbers 1-9
- Add within 20
- Identify pairs of numbers whose sum is 20
- Use TouchPoints as a strategy in computation

- Join together groups of objects to add
- Add using Pictorial TouchPoints
- Count on using TouchPoints

## Materials

- Extend Workbook (Page 18)
- Counters or manipulatives
- TouchMath’s Foam Numerals with TouchMath’s TouchPoints with or without pictures
- TouchMath’s number line
- Whiteboard, dry eraser markers, and dry eraser
- Board game that goes in sequential order
- Dice (optional)

## Step 1: Warm Up (5 min)

Pull out a board game of of your choosing that goes in sequential order. Show students that if you needed 10 spaces left to win the game and you rolled a 6, that you could identify the missing addend for the number of spaces left to win (4). Place a counter on a part of the board game and tell students the first number that was rolled. Ask them how many more would they need on the second dice to win the game.

## Step 2: Vocab Review (5 min)

Review addends, addition, addition sign, equals, sum, and counting on. Introduce the term “unknown” and “missing addend.” Explain that there will be a missing addend, or an “unknown number,” in the addition problems that they will need to figure out. Remind students that there are multiple ways to show adding but in this lesson you will be using counters and the TouchPoints to combine addends to find the sum. You will also use dots to represen the unknown addend. Sum is the answer to an addition sentence. It means the same as total, in all, and altogether.

## Step 3: Model (5 min)

On the whiteboard, write an addition problem (e.g. 10+4). Show that first this problem, students will solve like they did in the previous lesson: identify the larger addend, say the number, cross it out, and count on the TouchPoints of the second addend to find the sum (10, cross it out, 11, 12, 13, 14; 10+4=14). For the second problem, write 11 + __ = 13. Remind students to find the larger number (11), cross it out, and now count on and as they count, make a dot above the line until they get to 13 (2 total dots should be above the line). Explain that the dot is like a TouchPoint. It helps the quanitity to be added. Ask how many dots did they make, and to write 2 above the number line, and then read the equation (11+2=13). Show a few more problems with and without unknowns.

## Step 4: Guided Practice (5 min)

Now have students work in pairs or within groups. Give students an addition problem with sums no larger than 10 to start, using the Foam Numerals and TouchPoints. Once you have given the first problem (e.g. 5+3). Have students identify the larger number using their numbers lines, as needed (5). Then, have students place TouchPoints on the smaller number (3) and count on from the larger number after saying the number first (“6,7,8,” and repeat the whole fact: 5+3=8). Remind students when they get to paper and pencil, to cross out the larger number as you say the number aloud, then count on the second number. Give students addition problems with sums no larger than 10 and with a missing addend. Tell students to use their number lines, Foam Numerals and TouchPoints to help them solve for the missing addends. Increase sums to 20 during guided practice.

## Step 5: Student Practice (5 min)

Go to Student Workbook Page (18). Read the directions at the top of the page. Tell students to use the Foam Numerals and TouchPoints as needed, and to have their TouchMath number line vertical to identify the larger number of the addition problems. For the first problem, remind students to say the larger number (14) and then count on using the TouchPoints of the other number (15,16,17), and repeat the addition problem (14+3=17), then write the answer to the right of the equation sign on the line provided. Remind students to cross out the larger number before the count on the second number, so not to accidentally count the first number again. For the next problem, have students identify the larger number and then place a dot in the box when counting on: 12,13,14,15,16,17 (6 total dots should be in the box). Ask them to count how many dots they made and then to write the number in the box. For the third problem, have students count from 2 on to 12 and place dots in the box as they count on: 3,4,5,6,7,8,9,10,11,12 (10 total dots should be in the box). Again, ask them how many, and to write the number in the box (10), then repeat the addition math fact aloud (“10+2=12”). Repeat these steps for the next 4 problems, remembering to cross out the larger number before counting the TouchPoints on the second number (if provided).

## Step 6: Wrap Up (5 min)

To wrap up the lesson, review the learning objectives and core vocabulary words again and ask your students about their experience.