Word Problems: Addition and Subtraction

Students learn best by doing, especially with word problems where translating words into numbers can feel abstract. Using physical and social tools lets children test their thinking in real time, turning 'I'm not sure' into 'Let me show you.' Concrete models give students a way to catch mistakes before they become habits.

• Primary 2
• Mathematics
• 4 activities
• 25 min–40 min

Learning Objectives

1. Calculate the sum or difference to solve 1-step word problems involving quantities up to 1000.
2. Formulate a 2-step word problem that requires both addition and subtraction to find the solution.
3. Analyze a word problem to identify the relationship between known and unknown quantities using a bar model.
4. Compare the results of two different strategies for solving the same 2-step word problem.
5. Explain how clue words like 'more than' or 'left' indicate the operation needed in a word problem.

Problem-Based Learning

⏱ 30 min·Pairs

Manipulative Bars: Block Models

Pairs read a word problem, then use unifix cubes to build bar models showing quantities and relationships. They label parts, solve step-by-step, and write the equation. Pairs swap models with neighbors to verify solutions.

Prepare & details

How does a bar model help us understand the relationship between quantities in a word problem?

Facilitation Tip: During Manipulative Bars, ask students to label each bar with the story’s numbers before writing any equations.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Problem-Based Learning

⏱ 40 min·Small Groups

Role-Play Scenarios: Act and Model

Small groups pick props like toys or drawings to act out problems, such as buying fruit. One student narrates while others build bar models on paper during the skit. Groups solve and present their models to the class.

Prepare & details

What clue words tell us whether to add or subtract?

Facilitation Tip: In Role-Play Scenarios, freeze the action after each step and ask, 'What does this part of the story mean?' before modeling it with blocks.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Problem-Based Learning

⏱ 35 min·Small Groups

Clue Hunt Relay: Word Cards

Divide class into teams. Scatter cards with clue words and problems around the room. One student per team grabs a card, returns to build a bar model with group input, solves it, then tags the next teammate.

Prepare & details

How do we check that our answer makes sense in the context of the problem?

Facilitation Tip: For Clue Hunt Relay, hide clue words in different colors and have teams sort them into 'Addition,' 'Subtraction,' or 'Both' before solving.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Gallery Walk

⏱ 25 min·Small Groups

Gallery Walk: Peer Review

Students solve individual problems with bar models on chart paper and post them. In small groups, they walk the gallery, check if models match problems and answers make sense, then suggest improvements.

Prepare & details

How does a bar model help us understand the relationship between quantities in a word problem?

Facilitation Tip: During Check-It Gallery Walk, provide a checklist with 'Does the bar match the story?' and 'Can a peer explain each step?' to guide reviewers.

Setup: Wall space or tables arranged around room perimeter

Materials: Large paper/poster boards, Markers, Sticky notes for feedback

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

Teaching This Topic

Start with hands-on tools so students see how quantities combine or compare before moving to symbols. Avoid teaching clue words as rules, because words like 'more' can appear in both addition and subtraction situations. Instead, model flexible thinking by asking, 'What is changing here?' to focus on the story’s structure. Use peer talk to uncover misconceptions early and refine understanding together.

What to Expect

By the end of these activities, students will confidently draw bar models that match the problem story and choose the correct operation without relying on clue words alone. They will explain their steps, listen to peers, and revise their work when something doesn’t fit the story. Clear bar models and number sentences show their understanding.

Watch Out for These Misconceptions

Common Misconception

During Manipulative Bars, watch for students who draw bars based on clue words instead of the story’s meaning.

What to Teach Instead

Ask them to retell the story while pointing to each bar, then adjust the model so it matches their words rather than the clue word they chose.

Common Misconception

During Role-Play Scenarios, watch for students who act out the first part of a 2-step problem and stop there.

What to Teach Instead

Pause the role-play after the first step and ask, 'What happens next in the story?' Have them add new bars or blocks to show the second step before writing any equations.

Common Misconception

During Clue Hunt Relay, watch for students who sort clue words into 'Add' or 'Subtract' without considering the problem’s context.

What to Teach Instead

Have teams swap problems with another group and explain why their clue words led to a specific operation, using the story’s details to justify their choice.

Common Misconception

Assessment Ideas

Quick Check

Present students with a 1-step word problem. Ask them to draw a bar model, write the number sentence, and solve. For example: 'Sarah had 250 marbles. She won 120 more. How many marbles does she have now?'

Exit Ticket

Give students a 2-step word problem, such as: 'There were 300 red balloons and 250 blue balloons. 100 balloons popped. How many balloons are left?' Ask them to draw a bar model for the first step, write the number sentence, and then solve the second step, showing both calculations.

Discussion Prompt

Pose a word problem with ambiguous clue words. For example: 'John has 50 apples. Mary has 20 more apples than John. How many apples do they have together?' Ask students: 'What clue words help you decide what to do first? How can you check if your answer is reasonable?'

Extensions & Scaffolding

• Challenge: Give advanced students a 3-step problem where one step requires multiplication or division, and ask them to explain how to adjust the bar model.
• Scaffolding: Provide partially completed bar models with missing labels or numbers for students to finish before solving.
• Deeper exploration: Have students create their own word problems using a given set of numbers and clue words, then trade with peers to solve and review each other’s models.

Key Vocabulary

Bar Model	A visual drawing using rectangles to represent the known and unknown parts of a word problem, helping to show relationships like part-whole or comparison.
Part-Whole	A relationship where a whole quantity is made up of smaller parts. Addition combines parts to find the whole, while subtraction finds a missing part.
Comparison	A relationship where two quantities are compared to find the difference between them. This often involves subtraction.
Clue Words	Specific words in a word problem, such as 'altogether', 'in total', 'left', 'difference', that suggest whether to use addition or subtraction.