LESSON PLAN

Addition and Subtraction Facts to 20

Apothem Team

Grade 3 · Computational Fluency

LESSON AT A GLANCE

Warm-up

5 min

Explore

15 min

Consolidate

10 min

Practice

12 min

Exit ticket

3 min

Warm-up

Number talk: 9 + 7. Students solve mentally (no paper). Collect strategies: making 10 (9+1+6=16), doubles-plus-one (8+8=16), decompose 7 (9+1+6). All give 16. Which strategy is fastest for you? Strategies are personal: the goal is having at least one reliable strategy for every fact.

Explore

Fact family exploration: each group receives a set of three numbers (e.g., 6, 9, 15). Write all four related facts. Then: is there a strategy connection between the addition facts and the subtraction facts? (Yes: 15 - 9 can be solved by thinking 9 + ? = 15.)

Consolidate

Practice

Students complete a timed (or untimed) set of 20 mixed addition and subtraction facts to 20, self-assessing which facts are instant vs. still need a strategy. Exit ticket: write the fact family for 6, 7, 13.

Exit ticket

TIP Aim for 3-4 number talks per week. Each takes 5-10 minutes and builds the mental math flexibility that produces fluency. Consistency matters more than duration.

WORKED EXAMPLES

A student hesitates on 8 + 9. What strategy should they use?

Near-doubles: 8+8=16, so 8+9=17. Or making 10: 8+2=10, so 8+9=8+2+7=10+7=17. Or: 9+9=18, so 8+9=17. Multiple valid strategies. The student should choose the one that comes most naturally to them.

If a student knows 7+6=13, what 3 other facts do they know for free?

6+7=13 (commutativity), 13-7=6 (inverse), 13-6=7 (inverse). One addition fact gives 4 facts total.

MATERIALS

•Fact family triangles

•Number talk display

•Strategy anchor chart

•Flash cards (strategy-labelled)

•Ten-frames for bridging demonstration

WATCH FOR

!Students may not trust relational strategies and want to count on every time. Gradually remove that option during number talks: hands flat on the table, no finger counting.

!Students may know addition fluently but still count for subtraction. Explicitly connect: 15-8=? Think: 8+?=15. Using addition to solve subtraction is both valid and efficient.