Session 3 - Strategies to Add and Subtract within 20

Strategies to add and subtract within 20 - Grade 1

Progress Monitoring:

Directions: Addition Sets Progress Check

The progress check is used to assess or evaluate students’ understanding and demonstration of addition within 20.
The facilitator will use the progress check to identify if more practice should continue with addition before moving to part 2 which is focused on subtracting.
Answers are included in the Progress Check.
Print the activity for each student.
Read aloud the directions, if needed.
Students will be asked to “draw a number” meaning they make a visual representation of the numbers being calculated.
Record the student’s scores on the progress check, which will determine mastery of the strategy or if there is a need to reteach the strategy.

Green piggy bank and text

Visit the Resource Bank to learn more.

Lesson Activity: Model (20 - 30 minutes)

Activity: Subtraction Sets: Problems & Answers

Directions:

Before moving to Part 2 (Subtraction), the Addition Progress Check should be scored privately and any misconceptions or misunderstandings should be retaught for practice and address any errors.
Post or print the Big Idea Guiding Question (Slide 4)
See Slide 34, for a Warm-Up Activity.
Option for presenting the lesson:
1. Present the Addition & Subtraction Presentation Slides Part 2: Subtraction (slides 33-39)
2. Use the Subtraction Sets sheets in the steps throughout the toolkit and have students complete each one as you guide them through the practice.
Both options allow the lesson’s problem set to be printed for students to complete with guidance.
Students may complete activities with a partner or small group if more support is needed.
These problems have students practicing the strategies of counting on, making 20 using 10 frames, decomposing numbers within 10, and using the relationship of addition and subtraction.
If students get stuck understanding, here are some ideas for providing support for your students. These will intentionally lead them through the supported practice of the skill to grasp the learning and guide their thinking:
1. use hands-on materials to manipulate and put in groups.
2. ensure one-to-one counting correspondence is correct. If the student is having difficulty “seeing” numbers on the ten-frames, break down and put the 5s in two separate rows or use a rekenrek.
3. return to simpler problems with numbers adding within 10 and using one ten-frame.

Decorative question mark:

Why are students doing this/what are they getting out of it?

Students will practice subtracting within 20 using the making 10 strategy with guidance and may continue independent practice (may be a partner activity for more student support). Students will have many opportunities to demonstrate their thinking with the 5-group and ten-frame visual models.

Please Note

If this activity seems to be taking a long time, this would be a good breaking point.