Mathematics · Primary 2

Active learning ideas

Adding 2-Digit Numbers with Regrouping

Regrouping in two-digit addition requires students to move beyond counting by ones and see numbers as flexible groups of tens and ones. Active, hands-on tasks help them build mental images of exchanging ten ones for one ten or ten tens for one hundred, making the abstract concrete and lasting.

• MOE Syllabus Outcomes
• MOE: Numbers and Algebra - P2
• MOE: Whole Numbers - P2

• 20–30 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Simulation Game
• 30 min · Small Groups

Simulation Game: The Great Exchange Bank

One student acts as the 'Banker' while others are 'Accountants'. Accountants must trade 10 ones for 1 ten disk or 10 tens for 1 hundred disk to solve addition problems, physically moving the pieces across a mat.

Why do we need to regroup when the ones digits add up to 10 or more?

Facilitation Tip

In The Great Exchange Bank, circulate with a tray of place value disks so you can model exchanges instantly when a student hesitates.

What to look for

Give each student a card with an addition problem involving regrouping, such as 34 + 28. Ask them to solve it using the column algorithm and write one sentence explaining why they needed to regroup the ones.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 02

• Peer Teaching
• 20 min · Pairs

Peer Teaching: Regrouping Experts

After a short demo, students work in pairs. One student solves a subtraction problem with regrouping while the other acts as a 'coach', checking each step and asking 'Why did you rename that hundred?' before swapping roles.

How does the column method help us organise addition with regrouping?

What to look for

Present the problem 56 + 17 on the board. Ask students to show you with their fingers how many tens they would carry over after adding the ones column. Then, ask them to write the final sum on a mini-whiteboard.

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Activity 03

• Gallery Walk
• 25 min · Small Groups

Gallery Walk: Error Detectives

Display 'broken' addition and subtraction problems where the regrouping was done incorrectly. Students move in groups to identify the mistake and write a 'prescription' on how to fix it.

How can we use estimation to check whether our answer is reasonable?

What to look for

Pose the question: 'Imagine you are adding 45 + 37. How can you use estimation to predict if your final answer will be closer to 70, 80, or 90? Explain your thinking.'

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

A few notes on teaching this unit

Start with concrete tools like place value disks, then bridge to drawings, and finally to symbols. Always connect written steps to the physical action: when you write a '1' above the tens column, say aloud, 'This 1 means we have exchanged ten ones for one ten.' Avoid rushing to the algorithm before the concept is solid.

Students will confidently explain why regrouping is needed and perform the column addition algorithm accurately, using precise place value language. They will also catch and correct their own or peers' errors when the steps are made visible.

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Watch Out for These Misconceptions

• During The Great Exchange Bank, watch for students who move disks without recording the exchange in writing.

  Prompt them to pause after each move and write the new digit in the tens column on their whiteboard before continuing, linking the physical action to the symbol.

• During Peer Teaching: Regrouping Experts, watch for students who forget to reduce the tens digit after borrowing.

  Have peers point to the crossed-out tens digit and ask, 'What does this mark mean? Why did we cross it out?' This makes the reduction visible and verbal.

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Methods used in this brief

• Simulation Game
• Peer Teaching
• Gallery Walk