Mission 2 Add Whole Numbers

Overview

In this second of four missions, students solve whole-number addition problems using interactive games that highlight regrouping. They practice choosing efficient strategies and explain their reasoning.

Learning intentions

• Students will be able to add whole numbers with regrouping when needed.
• Students will use place value and properties of addition to solve and check sums.
• Students will be able to explain (or show) the strategy used for an addition problem.
• Students will be able to determine whether regrouping is necessary.

Success criteria

• I can solve addition problems with regrouping accurately.
• I can solve addition problems without regrouping accurately.
• I can use place value (or a written method) to justify my answer.
• I can check my work using a strategy (estimation, inverse, or composing/decomposing).

Curriculum links

• Solve multi-digit whole number addition using place value understanding and regrouping.
• Use addition properties and mental math strategies to compute efficiently.
• Explain calculation strategies and check reasonableness of results.

Lesson structure (30 minutes)

1. 0–4 min: Warm-up—“Spot the regroup” The teacher displays short addition problems (e.g., 234 + 126; 352 + 114; 410 + 205). Students quickly hold up a sign: “Regroup” or “No regroup,” then share one reason (based on place value). Teacher reinforces: regrouping happens when a place value column reaches 10 (ones) and must transfer to tens, then hundreds if needed.

2. 4–10 min: Mini-lesson—strategy ladder Teacher models one problem with three quick representations: manipulatives (base-ten blocks), a number bond/part-part-whole sketch, and a written vertical method. Emphasize a consistent approach students can reuse: align place values, add ones, regroup to tens if necessary, then add tens (and hundreds if present).

3. 10–17 min: Game 1—Regroup Race (pairs) Students work in pairs with base-ten blocks or bundling cubes. Each pair draws 4–6 addition cards and chooses their strategy before solving. Rules: For each card, they must (a) solve, (b) indicate whether regrouping occurred, and (c) show a quick check (estimate or inverse using subtraction). Teacher circulates using a quick checklist: accuracy, place value alignment, and whether they regroup correctly.

4. 17–24 min: Game 2—Make It True (small groups of 3) Groups get a “sum target” and three addend cards. Example: Target 560; addends 240, 130, and a choice card that completes the sum. Students compute the missing addend using addition reasoning (then verify). This reinforces both “with regrouping” and “without regrouping” paths depending on the values. Students write one sentence explaining how they knew regrouping was or was not required.

5. 24–28 min: Whole-class debrief—strategy share Students share one problem where regrouping was needed and one where it wasn’t. Teacher records common strategies on the board (decompose, compose, estimation check, inverse check). Teacher probes: “What did you do in the ones place? Where did the regroup go?”

6. 28–30 min: Exit ticket—2 problems + explain Students complete two addition problems at their level: one requiring regrouping and one not requiring regrouping. They include a one-line explanation: “I regrouped because…” or “I didn’t regroup because…”

Resources

• Base-ten blocks, bundling cubes, and place-value mats (ones/tens/hundreds columns)
• Regroup Race addition card set (mix of regrouping and non-regrouping problems)
• Make It True target-and-addend card set
• Student whiteboards or scrap paper for quick checks
• Regroup/No Regroup response cards or finger signals
• Teacher checklist for conferencing during games
• Exit ticket slips (two problems per student)

Assessment

• Formative: teacher observation during both games (accurate regrouping and correct place-value reasoning).
• Formative: exit ticket correctness plus the one-line justification about regrouping.
• Optional quick spot check: ask one student to explain a regroup step using place value language.

Differentiation

• Support: pre-pair students for peer teaching; assign one “strategy leader” in each pair and provide manipulatives for students who need concrete support.
• Support: offer a place-value scaffold (partially completed vertical alignment template) for written work.
• Target: students use their preferred representation (blocks, drawings, or number sentences) before writing the final sum.
• Extension: students add a second method for one card (e.g., partial sums or estimation-first) and explain which method is more efficient and why.
• EAL: sentence frames for explanations (“I regrouped in the __ place because __.” “I checked by estimating/inversing.”). Keep vocabulary consistent with place value terms.
• SEN: limit card sets to fewer problems but require thorough work on each; provide “regrouping transfer” arrows on the mat.

Extension (optional)

• Advanced learners: Create a real-world story problem that requires addition and clearly decide whether regrouping is necessary. Students write:
• the story (e.g., books, points scored, snacks counted),
• the addition equation,
• the computation with at least one regroup step highlighted,
• a quick check method and a one-sentence answer justification.
• Share-out: volunteers read their story problems while classmates identify if regrouping is required and why.