Add Within Twenty

Overview

In this 30-minute lesson, students practice adding two numbers within 20 using objects, drawings, counting on, and make-ten strategies. The lesson builds from familiar counting and addition within 10 toward choosing and explaining an efficient strategy. The primary task is designed for kindergarten and Grade 1 learners, with flexible entry points for students in Grades 2–5 who need additional support.

Learning intentions

• Students will be able to add two numbers with a total of 20 or less.
• Students will be able to represent an addition problem with objects, a drawing, or a number line.
• Students will be able to use counting on or make-ten strategies.
• Students will be able to explain how they found an answer.

Success criteria

• I can solve at least four addition problems within 20.
• I can use objects, a drawing, a number line, or a strategy to show my thinking.
• I can count on or make ten to help me add.
• I can explain my strategy to a partner or teacher.

Curriculum links

• Operations and Algebraic Thinking — fluently add and subtract within 5.
• Operations and Algebraic Thinking — add and subtract within 20, with fluency within 10 and appropriate strategies.
• Operations and Algebraic Thinking — relate counting to addition by counting on.
• Operations and Algebraic Thinking — find numbers that make 10 when added to a given number.

Lesson structure (30 minutes)

1. 0–4 min · Hook and connect. Teacher opens the opening addition challenge and displays 8 counters and 5 more, asking, “How many are there altogether? How could we find out without starting at 1?” Students estimate, share a strategy, and connect adding with combining groups.

2. 4–9 min · Model strategies. Teacher uses the strategy slides to model 8 + 5 with counters, a ten-frame, and a number line: count on from 8, then make ten by moving 2 from 5 to 8. Students build or draw each representation and describe what changes and what stays the same.

3. 9–13 min · Guided practice. Teacher displays two problems from the guided-practice slides, such as 6 + 3 and 7 + 6, and prompts students to select a tool or strategy; check answers by counting all or using a related representation. Students solve with a partner, point to their steps, and explain using the frame, “I started with __. I added __. The total is __.”

4. 13–24 min · Independent practice. Teacher distributes the addition within 20 practice sheet and places counters, ten-frames, and number lines at an accessible work area. Students solve at least four problems, choosing objects, drawings, counting on, or make-ten; the teacher conferences with students and records whether they represent, solve, and explain each problem.

5. 24–27 min · Share and compare. Teacher returns to the strategy comparison slides and selects two student solutions, asking, “Which strategy helped? Did both methods give the same total? How do you know?” Students turn and talk, then share one strategy or observation with the class.

6. 27–30 min · Exit check and close. Teacher shows the final prompt on the exit prompt slide: 9 + 4 = __. Students solve it independently on the back of the worksheet or with a quick drawing, then complete the sentence, “I used __ because __.” Collect responses and restate the goal: addition can be shown and solved in more than one way.

Resources

• the addition strategy slide deck
• the addition within 20 practice sheet
• Connecting cubes or counters
• Double ten-frames
• Open number lines
• Pencils, crayons, and erasers
• Large-print visual strategy cards
• Optional dry-erase boards and markers

Assessment

• During modeling and guided practice, ask students to show 8 + 5 in two ways and listen for accurate counting on or make-ten reasoning.
• During worksheet practice, check whether each student represents the problem, finds a total within 20, and can explain a strategy. Prompt rather than correct: “What number will you start with?” or “How could you make ten?”
• Use the final 9 + 4 exit response to identify next steps: students needing concrete support, students ready for addition within 10 fluency, and students ready to solve mentally.

Differentiation

• Support: Provide problems within 10, counters, ten-frames, and a marked number line. Begin with the larger addend, model touching or moving one object per count, and reduce the worksheet to four clearly spaced problems.
• Developing independence: Offer a choice of visual strategy cards showing count all, count on, and make ten. Use oral directions one step at a time and ask students to explain verbally, point, draw, or use an augmentative communication system.
• Dyslexia-friendly access: Use an uncluttered worksheet, large print, high contrast, generous spacing, simple numerals, and minimal written directions. Read every direction aloud, preview symbols and vocabulary, and allow students to answer orally or use manipulatives instead of copying explanations.
• Advanced learners: Students solve selected problems mentally, including 8 + 7 and 9 + 6, and explain why make-ten or a related known fact is efficient. Invite them to create an addition problem within 20 that can be solved in two different ways and compare the strategies.

Extension

• Students generate three addition problems within 20 that have the same total and represent each with a drawing or equation.
• Students explain how knowing a fact such as 6 + 4 = 10 helps solve a new problem such as 6 + 7.