Adding and Subtracting

Overview

This 60-minute lesson is designed for Grade 2 students in British Columbia to master addition and subtraction of 1- and 2-digit numbers with sums or differences up to 100. It uses the BC Curriculum’s focus on concrete, pictorial, and mental strategies to build a solid number sense foundation. The lesson includes relevant activities, assessment opportunities, and differentiation ideas for a split Grade 2/3 class in Saskatchewan, ensuring alignment with BC standards while considering diverse learner needs.

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Curriculum Connections

British Columbia Curriculum – Mathematics (Grade 2):

• Number Concepts and Operations:
  • Use place value to add and subtract 2-digit numbers, with and without regrouping (2.N.1)
  • Solve addition and subtraction problems involving numbers to 100 using concrete materials, pictures, and mental strategies (2.N.2)
• Reasoning and Analyzing:
  • Explain and apply mental mathematics strategies (2.R.1)
• Communicating and Representing:
  • Represent numbers and number operations in multiple ways (2.C.1)

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Learning Objectives

By the end of this lesson, students will be able to:

1. Add and subtract 1- and 2-digit numbers with sums or differences up to 100 using concrete objects and pictorial representations.
2. Demonstrate understanding of place value to solve addition and subtraction problems involving regrouping.
3. Explain their problem-solving strategy verbally or through drawings.
4. Apply mental math strategies such as counting on/back and using friendly numbers.

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Materials Needed

• Base ten blocks (ones and tens)
• Number cards (1-100)
• Whiteboards and markers
• Worksheets with pictorial problems (e.g., pictures of objects to add/subtract)
• Counters or small objects (e.g., beans, buttons)
• “Number Bond” templates
• Interactive Smartboard or chart paper for modelling

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Lesson Schedule and Activities

1. Warm-Up (10 minutes)

• Activity: “Number Talks” Mental Math Routines
  • Present addition and subtraction problems within 20 on the board (e.g., 18 + 5, 30 - 7).
  • Encourage students to share mental strategies aloud. Prompt for counting on, making ten, or doubles facts.
  • Emphasise multiple ways to solve, reinforcing flexible thinking.

2. Introduction and Modelling (10 minutes)

• Teacher Modelling:
  • Use base ten blocks to show addition and subtraction with regrouping. Example: 46 + 27
  • Demonstrate decomposing numbers (e.g., 27 = 20 + 7), then add tens and ones separately using blocks.
  • Show and explain subtraction with regrouping (e.g., 52 - 18), exchanging a ten for ones.
  • Draw pictorial representations (tens rods and ones dots) alongside the blocks.

3. Guided Practice (15 minutes)

• Activity: “Concrete to Pictorial” Stations
  Set up 3 stations:
  1. Concrete Station: Students use base ten blocks to solve given addition and subtraction problems with teacher support.
  2. Pictorial Station: Work on worksheets to draw tens rods and ones dots to add or subtract numbers.
  3. Number Bonds: Create number bonds to represent addition and subtraction facts visually.
• Students rotate every 5 minutes in groups of 6-7 to experience all representations.

4. Independent Practice (15 minutes)

• Activity: Whiteboard Challenge
  • Students receive randomly selected number cards (1-100).
  • They write and solve their own addition or subtraction problem using concrete or pictorial methods and show their work on whiteboards.
  • Peers come around to explain their thinking, using sentence stems like “I subtracted by...” or “I added using…”
  • Teacher circulates to observe, support, and prompt deeper reasoning.

5. Reflection and Sharing (5 minutes)

• Invite 3-4 volunteers to explain how they solved one of their problems, referencing either concrete, pictorial or mental strategies.
• Highlight diverse strategies and reinforce the value of explaining thinking.

6. Formative Assessment (5 minutes)

• Exit Ticket:
  Pose two problems (one addition, one subtraction, both within 100) on the board. Students solve on a small slip and indicate:
  • Method used (concrete, pictorial, or mental)
  • One sentence explaining their strategy
• Collect slips to gauge individual understanding and plan next steps.

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Differentiation Strategies

Learner Profile	Strategy	Grade 3 Extension Idea
Struggling Learners	Provide additional manipulative support; pairing with peers for modeling and encouragement. Use number lines as step-by-step visual aids.	Introduce 3-digit addition/subtraction through the same concrete-pictorial approach.
English Language Learners (ELL)	Use visual cues, picture cards, and sentence stems to scaffold language development. Use bilingual number labels if helpful.	Encourage recorded verbal explanations or drawings instead of writing.
Advanced Learners	Challenge with missing addend problems (e.g., “___ + 15 = 63”) and story problems requiring multi-step operations.	Introduce simple word problems involving real-life financial scenarios, e.g., buying items and giving change.

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Teacher Notes

• Monitor students’ use of place value language ("tens," "ones," "exchange") to deepen conceptual understanding.
• Reinforce the BC competency of communicating mathematical thinking clearly by encouraging students to describe their methods.
• Use formative data from exit tickets to tailor follow-up lessons focusing on regrouping or mental strategies.
• Consider flexibility for the Grade 3 students by increasing complexity of numbers or introducing more abstract representations (e.g., number lines).

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This lesson blends hands-on manipulatives with pictorial and mental approaches to develop robust addition and subtraction skills consistent with British Columbia’s Mathematics Curriculum, engaging students through varied modalities and encouraging confident math talk.