Lesson 22: Subtraction within 10
Lesson Objectives
- Use the Concrete-Representational-Abstract (CRA) sequence
- Apply TouchPoints on both numerals
- Relate subtraction to backwards counting
- Recognize patterns in differences
- Count backward within 10
Materials
- Extend Workbook (Page 22)
- Counters or manipulatives
- TouchMath’s Foam Numerals and TouchPoints with or without pictures
- Open ten-frames
- Linking cubes
Step 1: Warm Up (5 min)
Explain to students that when we say and write subtraction sentences, we use minus to mean take away. Repeat the number sentence: 3 minus 1 = 2. The answer, 2, is the difference. Take out linking cubes to illustrate subtraction. Take out 5 cubes linked and show students. Show the students as you take away 3 cubes. Ask how many cubes you have left (Yes, 2 cubes.). The number sentence is 5 minus 3 = 2.
Step 2: Vocab Review (5 min)
Introduce new vocabulary: subtraction, difference, minus, part, subtract, take away, whole. Explain to students that they will subtract a part from the whole by taking away one part. Remind them that when they added, they put the parts together. When they joined the parts, they found the sum, or the whole. Now, when they subtract, they will start with the whole and take away one part. When you take away one part, you have one part left. It is called the difference. Show basic examples: hold up three fingers, take one away, and now you have 2 fingers left. So, 3 fingers minus 1 finger equals 2 fingers left, or 3 take away 1 equals 3. Show various examples with counters and manipulatives.
Step 3: Model (5 min)
Take out counters and TouchMath’s Foam Numerals and TouchPoints. Write a subtraction problem on the board (4-2) and show 4 counters and then ask students how many should be taken away (2). Take away 2 and ask how many are left? (2). Ask students to repeat the subtraction number sentence: 4-2=2. Give real examples of this (e.g. I had 4 apples, and two apples were eaten. Two apples were left). Show the TouchMath Foam Numeral 4 and 2. Place two TouchPoints on the Numeral. Tell students to take the first Numeral, say it, pick it up, and remove it and then count backwards on the TouchPoints of the 2 (3, 2). Tell students to physically remove the TouchPoints on the 2, since you are “taking away” 2. Then repeat the math fact (4-2=2). Show a few examples using both the counters and Foam Numerals and TouchPoints.
Step 4: Guided Practice (5 min)
Take out am open ten-frame and place fill out the frame (10 total dots). Ask students to count the dots and identify how many they are starting with (10), then ask students to take 2 dots away, and ask how many are left. Repeat these a few times taking away a different amount each time, and asking how many are left. Then, have students work together with their TouchMath Foam Numerals and TouchPoints to solve subtraction problems within 5, and then within 10, following the correct steps: 1) say the larger/first number, 2) pick it up and remove it, 3) count backward on the TouchPoints of the other number, 4) repeat the math subtraction fact (e.g. “3-2=1”).
Step 5: Student Practice (5 min)
Go to Student Workbook Page (22). Read the directions at the top of the page. Tell students they will be solving various subtraction problems. In the first problem, tell students that once they know how many they must take away, that a good trick is to cross off the exact number of images that are to be taken away (e.g. 4 milkshakes) and then circle the group that is left (4 milkshakes left). You can also have students write the subtraction sentence below the line for further practice (8-4=4). Have students work independenly on the page, helping as needed. Remind students to cross off the number requested to take away and to write how many are left on the line provided. When they get to the 5-frame with subtraction sentences (5-2 and 3-1), remind them to cross off the first number, then count backward on the TouchPoints of the other number. For example, cross off the 5, count backwards on the 2 (4, 3). Your answer is 3. Then, have them repeat the math fact aloud to build automaticity (5-2=3). Repeat this step for the next 5-frame subtraction problem.
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. Circle back to those real-life connections and experiences.
