Subtraction with Regrouping

Learning Objectives

Aligned with British Columbia Mathematics Curriculum (Grade 2), this lesson targets the following:

• Number Concepts and Operations

  • Use place value to add and subtract two-digit numbers (2-NS-01)
  • Solve subtraction problems involving regrouping (borrowing) (2-NS-02)

• Mathematical Processes and Competencies

  • Apply reasoning to solve problems and explain thinking (2-MP-01)
  • Communicate mathematical ideas clearly (2-MP-04)

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Materials Needed

• Base-ten blocks (ones and tens rods)
• Whiteboard and markers
• Individual mini whiteboards for students
• Prepared subtraction worksheet (included below)
• Sticky notes or small cards labelled "Tens" and "Ones"
• Counters or small objects for hands-on practice

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Lesson Timeline (40 Minutes)

1. Introduction (5 minutes)

• Begin by reviewing place value (tens and ones) using base-ten blocks.
• Demonstrate with a two-digit number, e.g., 43 = 4 tens + 3 ones.
• Explain today's goal: subtracting two-digit numbers where you sometimes need to regroup (borrow from the tens place).
• Connect to real-life example: "If you have 43 apples and you give away 27, how many do you have left?"

2. Guided Teaching & Modelling (10 minutes)

• Model subtraction without regrouping first: 54 – 21. Use base-ten blocks to subtract tens and ones separately.
• Then introduce subtraction requiring regrouping: 42 – 18.
  • Use base-ten blocks to show 42 as 4 tens and 2 ones.
  • Explain that since 2 ones are not enough to subtract 8 ones, you must break one ten into 10 ones (regrouping).
  • Show the regrouping process visually with blocks and write the corresponding subtraction algorithm on the board.
• Write the subtraction vertically to emphasize place values:

    3  12
   -1   8
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• Walk through the subtraction step-by-step.

3. Collaborative Practice (10 minutes)

• Distribute mini whiteboards and base-ten blocks to students.
• Give 2 or 3 similar subtraction problems (including both regrouping and non-regrouping types). Examples:
  • 63 – 27
  • 51 – 35
  • 74 – 48
• Guide students to use blocks and write the subtraction vertically, modelling regrouping.
• Encourage students to explain their thinking to a partner using correct place value language (tens, ones, borrowing).

4. Independent Practice (10 minutes)

• Hand out the worksheet (formatted and scaffolded for understanding, see below).
• Students complete subtraction problems on their own, using the space to show regrouping steps.
• Circulate to assist, prompt explanations, and offer positive reinforcement.

5. Review & Reflection (5 minutes)

• Select a few students to demonstrate one regrouping problem on the board.
• Ask:
  • "Why do we regroup?"
  • "How do tens change when we regroup?"
  • "What does the top number represent after regrouping?"
• Reinforce that subtraction with regrouping helps us subtract tens and ones correctly by borrowing.
• Wrap up with verbal praise and encourage students to think about subtraction in everyday situations.

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Assessment and Success Criteria

• Observation of students using place value terms appropriately during partner talk (formative)
• Worksheet accuracy and completeness (formative)
• Ability to explain regrouping steps clearly to peers or the teacher (summative)

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Worksheet: Subtracting Two-Digit Numbers with Regrouping

Problem	Tens	Ones	Borrow?	Explanation (Write what you did)	Answer
1) 53 – 25
2) 61 – 38
3) 74 – 39
4) 85 – 47
5) 92 – 56

Instructions: Break each number into tens and ones in the boxes. Indicate if you need to borrow (regroup). Write in your own words what you did to solve the problem, then write the final answer.

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Formatting notes:

• Draw vertical subtraction format beside each problem for students to write digits clearly.
• Provide space to draw base-ten blocks for those who want to illustrate.
• Include a small reminder box at the top of the worksheet:
  "When you can't subtract the ones place, borrow 1 ten and change it to 10 ones."

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Differentiation and Extensions

• Support: Provide additional base-ten blocks and one-on-one assistance for students struggling with place value concepts.
• Challenge: Include three-digit subtraction with regrouping for early finishers or use word problems requiring subtraction and explaining regrouping steps.
• English Language Learners: Use visual aids and sentence starters for explanations, e.g., "I borrowed ___ because ___."

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This lesson plan not only targets curriculum-aligned learning goals, but also incorporates multi-sensory approaches, peer collaboration, and emphasis on mathematical communication, instilling deep conceptual understanding of subtraction with regrouping for BC grade 2 students.