Adding and Subtracting to 20

Overview

In this 15-minute lesson, students practice addition and subtraction within 20 using quick, hands-on representations and number sentences. They will connect concrete objects to drawings and written equations.

Learning intentions

• Students will be able to add within 20 using objects, drawings, and number sentences.
• Students will be able to subtract within 20 using objects, drawings, and number sentences.
• Students will be able to explain how they found an answer using words like “more,” “less,” “together,” and “take away.”

Success criteria

• I can solve an addition problem within 20 and show it with objects or a drawing.
• I can solve a subtraction problem within 20 and show it with objects or a drawing.
• I can write a number sentence that matches my model.

Curriculum links

• Understand addition and subtraction within 20 using objects, drawings, and equations.
• Use strategies and relate counting to solving simple addition and subtraction problems.
• Write equations that represent addition and subtraction situations.

Lesson structure (15 minutes)

1. 1 min — Warm-up counting Teacher shows cards with numbers 0–20. Students chorally count up or down by 1 based on a prompt (e.g., “Start at 7 and count to 12,” “Count back from 15 to 10”).

2. 3 min — Mini-lesson with models (add) Teacher models a problem using counters: “There are 9 counters. More counters are added. Now there are 14. How many were added?” Students watch the teacher: separate the “before” and “after,” count on to find the missing addend, and then write an addition equation that matches the model.

3. 3 min — Guided practice (add to 20) On the board, teacher writes two addition stories with object pictures (or pre-arranged counters). Students use fingers or small personal whiteboards to solve and show the equation. Teacher circulates and prompts: “What does your model show? Is the answer more or less?”

4. 2 min — Transition and quick reset Students put counters away, do a 10-second shoulder stretch, and repeat a short chant: “Add means together. Subtract means take away.”

5. 3 min — Mini-lesson with models (subtract) Teacher models subtraction: “There are 13 counters. Take away 5. How many are left?” Teacher moves counters into a “take away” group, counts what remains, and writes the subtraction equation.

6. 2 min — Partner practice (one each) In pairs, students draw a quick picture model for one addition and one subtraction problem given by the teacher (within 20). They write the matching equation on their own paper or boards.

7. 1 min — Exit check Teacher reads two final problems aloud. Students hold up the correct number on fingers or show on a board, then teacher asks one student to explain their strategy briefly.

Resources

• Counting counters (two colors if possible), or small unifix cubes
• Personal whiteboards or paper, plus markers/chalk
• Number cards 0–20
• Picture cards or simple drawings for “together/more” and “take away/left”
• Projector or board to display the teacher’s model and number sentences
• Partner worksheet or scratch paper with two blank equation lines
• Timer (to keep the lesson within 15 minutes)

Assessment

• Formative checks during guided practice: teacher listens for correct explanations and correct equations.
• Partner practice: review written number sentences to confirm they match the model.
• Exit check: identify common errors (off-by-one counting, mixing up add vs. subtract) and note which students need reteaching.

Differentiation

• Support: Provide a sentence frame (“I have ___. I add/take away ___. I have ___ left/now.”) and fewer story steps; use ten-frames or grouped counters if available.
• Support for SEN: Allow counting strategies with counters and reduce to one operation type first (either add or subtract) before mixing both.
• Extension: Give a two-step story within 20 (e.g., “First add, then take away”) and ask students to write two equations and choose which equation gives the final answer.
• EAL: Use gestures with “together/more” and “take away/left,” and encourage students to point to parts of the model while saying the numbers.