Mathematics · Primary 1

Active learning ideas

Subtraction with Regrouping (within 100)

Active learning helps students grasp subtraction with regrouping because it makes abstract borrowing concrete. When children manipulate physical blocks or write with visual cues, they connect the written steps to the real value of numbers. This hands-on work builds the mental images needed to move from blocks to mental math later.

• MOE Syllabus Outcomes
• MOE: N(v).7
• MOE: N(v).8

• 20–35 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Think-Pair-Share
• 30 min · Small Groups

Manipulatives: Base-10 Block Subtraction

Provide base-10 blocks and place value mats. Students build the minuend, then trade a ten rod for ten ones if needed before subtracting. Record the steps on mini-whiteboards and discuss as a group.

What do we do when there are not enough ones to subtract from?

Facilitation Tip

During Base-10 Block Subtraction, circulate to ensure students trade one ten rod for ten unit cubes only when the ones place lacks enough.

What to look for

Provide students with a subtraction problem like 42 - 15. Ask them to solve it and draw a picture using base-ten blocks to show how they regrouped the tens and ones.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 02

• Think-Pair-Share
• 20 min · Pairs

Pair Game: Regrouping Roll and Subtract

Pairs roll two dice to form two-digit numbers, subtract with regrouping using drawings or blocks if needed. First to correctly solve five problems wins a point. Switch roles after each round.

How do we show regrouping in our written working?

Facilitation Tip

In Regrouping Roll and Subtract, pair students so they verbalize each step aloud, which reinforces the language of borrowing.

What to look for

Write 53 - 27 on the board. Ask students to show thumbs up if regrouping is needed in the ones place. Then, ask them to write the new value of the tens and ones digits after regrouping on a mini-whiteboard.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 03

• Think-Pair-Share
• 35 min · Whole Class

Whole Class: Story Problem Chain

Project a multi-step story problem requiring regrouping, like buying toys. Students solve in sequence, passing solutions around the class. Teacher pauses for regrouping demos on board.

Does regrouping change the total value of the number? Why?

Facilitation Tip

During Story Problem Chain, pause after each problem to ask, 'How did we adjust the tens and ones?' to keep the focus on regrouping.

What to look for

Pose the question: 'Why is it important to write down the regrouping step when we solve subtraction problems?' Facilitate a brief class discussion, guiding students to explain how it helps avoid errors and keeps track of the number's value.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 04

• Think-Pair-Share
• 25 min · Individual

Individual: Visual Regrouping Sheets

Give worksheets with tens frames filled for numbers. Students cross out to show borrowing, then complete subtraction. Self-check with answer overlays before sharing one with partner.

What do we do when there are not enough ones to subtract from?

Facilitation Tip

On Visual Regrouping Sheets, remind students to circle the regrouped digit and write the new tens and ones values above the original digits.

What to look for

Provide students with a subtraction problem like 42 - 15. Ask them to solve it and draw a picture using base-ten blocks to show how they regrouped the tens and ones.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

A few notes on teaching this unit

Start with base-ten blocks to make the exchange visible, then link the physical trade to the written algorithm. Use consistent language: 'trade one ten for ten ones,' not 'borrow,' to avoid confusion with borrowing in everyday contexts. Avoid rushing to abstract symbols; give students time to describe the regrouping process in their own words before formalizing it.

By the end of the series, students should correctly solve two-digit subtraction problems that require regrouping and explain why they borrowed. They should also record regrouping steps neatly and verify their answers with tools like base-ten blocks or number lines.

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Watch Out for These Misconceptions

• During Base-10 Block Subtraction, watch for students who think exchanging 1 ten for 10 ones changes the total value.

  Have students count the total value before and after the trade using the blocks, then record both counts to prove the value stays the same. Ask, 'How many tens and ones do you have now?' to reinforce equivalence.

• During Regrouping Roll and Subtract, watch for students who assume regrouping is impossible when the tens digit is zero.

  Use the dice rolls to build the minuend with blocks first, then guide students to trade a ten for ones only if the ones column is insufficient. Ask, 'Can we take a ten from the tens place here?' and let them test with the blocks.

• During Visual Regrouping Sheets, watch for students who subtract ones first regardless of regrouping need.

  Have students circle the ones column and write 'Trade needed?' before solving. Use a number line alongside the sheet so they jump back in ones first only when regrouping, otherwise tens first.

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Methods used in this brief

• Think-Pair-Share