Subtraction of 3-Digit Numbers for Primary 3

Class: Primary 3
Term: 1st Term
Week: 6
Age: 8 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Number and Numeration
Previous Lesson: Fraction, Division of Concrete Objects Into, 1 1.
Topic: Subtraction
Subject Matter: Subtraction of 3-digit numbers with regrouping, Subtraction of fractions with the same denominator

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Subtract 3-digit numbers with regrouping accurately.
• Subtract fractions with the same denominators.

Affective Domain:

• Show appreciation for the importance of accurate subtraction in daily life.
• Demonstrate confidence in solving subtraction problems involving regrouping and fractions.

Psychomotor Domain:

• Accurately solve subtraction problems on the board or in their notebooks.
• Demonstrate the process of regrouping when subtracting 3-digit numbers.

Social Domain:

• Work collaboratively with peers to solve subtraction problems.

Reference Materials

The following resources were used in planning this lesson:

• 9 Years Basic Education Curriculum for Primary 3 Mathematics
• State Unified Scheme of Work for Primary 3 Mathematics
• New General Mathematics for Primary Schools Book 3

Instructional Materials

The teacher will teach this lesson with the aid of:

• Number charts
• Place value charts
• Fraction cut-outs or diagrams
• Whiteboard/Blackboard
• Markers/Chalk

Rationale for the Lesson

This lesson enables pupils to master essential subtraction skills, which are fundamental for everyday calculations such as managing money and understanding quantities. Understanding these concepts helps pupils build a strong foundation for more complex mathematical operations in the future.

Prerequisite/Previous Knowledge

Pupils can subtract 2-digit numbers without regrouping and identify simple fractions.

Lesson Content/Board Summary

Subtraction

Subtraction of 3-Digit Numbers with Regrouping

Subtraction is the process of taking one number or quantity away from another. Regrouping (or borrowing) in subtraction is necessary when a digit in the minuend (top number) is smaller than the corresponding digit in the subtrahend (bottom number) in the same place value column.

Steps for subtracting 3-digit numbers with regrouping:

• Start subtracting from the Ones column.
• If the top digit is smaller, regroup (borrow) 1 ten from the Tens column (leaving 1 less ten) and add 10 to the Ones digit.
• Subtract the Ones.
• Move to the Tens column. If the top digit is smaller (after regrouping), regroup 1 hundred from the Hundreds column (leaving 1 less hundred) and add 10 to the Tens digit.
• Subtract the Tens.
• Finally, subtract the Hundreds.

Example 1: Subtract 345 from 672

672

– 345

—–

Solution:

Step 1: Subtract the Ones column. We cannot subtract 5 from 2. Regroup 1 ten from 7 tens in the Tens column, leaving 6 tens. Add 10 to the 2 ones, making it 12 ones.
12 – 5 = 7

Step 2: Subtract the Tens column. We now have 6 tens. Subtract 4 tens from 6 tens.
6 – 4 = 2

Step 3: Subtract the Hundreds column. Subtract 3 hundreds from 6 hundreds.
6 – 3 = 3

Answer: 327

Example 2: Find the difference between 500 and 238

500

– 238

—–

Solution:

Step 1: Subtract the Ones column. We cannot subtract 8 from 0. We need to regroup from the Tens column, but it’s also 0. So, we regroup from the Hundreds column. Regroup 1 hundred from 5 hundreds, leaving 4 hundreds. The 1 hundred becomes 10 tens in the Tens column.
Now, regroup 1 ten from 10 tens (leaving 9 tens) and add 10 to the 0 ones, making it 10 ones.
10 – 8 = 2

Step 2: Subtract the Tens column. We now have 9 tens. Subtract 3 tens from 9 tens.
9 – 3 = 6

Step 3: Subtract the Hundreds column. We now have 4 hundreds. Subtract 2 hundreds from 4 hundreds.
4 – 2 = 2

Answer: 262

Subtraction of Fractions with the Same Denominator

Subtracting fractions with the same denominator means taking away a part of a whole where the total number of parts remains unchanged. Only the numerators are subtracted.

Formula:

When subtracting fractions with the same denominator, subtract the numerators and keep the denominator the same.

^a/_c – ^b/_c = ^{(a – b)}/_c

• a and b are the numerators (the top numbers).
• c is the common denominator (the bottom number).

Example 1: Subtract ²/₆ from ³/₆

³/₆ – ²/₆

Solution:

Step 1: Identify the numerators and the common denominator.
Numerators: 3 and 2. Denominator: 6.

Step 2: Subtract the numerators.
3 – 2 = 1

Step 3: Keep the denominator the same.
The denominator is 6.

Answer: ¹/₆

Example 2: Calculate ⁷/₈ – ³/₈

Solution:

Step 1: Identify the numerators and the common denominator.
Numerators: 7 and 3. Denominator: 8.

Step 2: Subtract the numerators.
7 – 3 = 4

Step 3: Keep the denominator the same.
The denominator is 8.

Answer: ⁴/₈ (which can be simplified to ¹/₂)

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Subtraction

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to recall what subtraction means by giving simple examples like “If you have 5 oranges and eat 2, how many are left?”.
Pupils’ Activity: Pupils respond to the greetings and answer the questions based on their previous knowledge.
Learning Point: Pupils recall the basic concept of subtraction.

Step 2: Presentation of 3-Digit Subtraction with Regrouping

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher introduces subtraction of 3-digit numbers with regrouping, explaining when and how to regroup using a place value chart and a worked example on the board (e.g., 672 – 345).
Pupils’ Activity: Pupils listen attentively, observe the demonstration, and ask questions for clarification.
Learning Point: Pupils understand the concept and steps of regrouping in 3-digit subtraction.

Step 3: Guided Practice (3-Digit Subtraction)

Time: 7 minutes
Teaching Skill: Coaching/Practice
Teacher’s Activity: The teacher writes another example (e.g., 500 – 238) on the board and guides pupils step-by-step through the solution, encouraging them to participate in each step.
Pupils’ Activity: Pupils actively participate in solving the example on the board and in their notebooks.
Learning Point: Pupils practice and reinforce their understanding of 3-digit subtraction with regrouping.

Step 4: Presentation of Fraction Subtraction

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher introduces subtraction of fractions with the same denominator using fraction cut-outs or diagrams. The teacher explains that only the numerators are subtracted while the denominator remains the same, providing the formula and an example (e.g., ³/₆ – ²/₆).
Pupils’ Activity: Pupils observe the fraction diagrams and listen to the explanation of subtracting fractions.
Learning Point: Pupils understand how to subtract fractions with common denominators.

Step 5: Guided Practice (Fraction Subtraction)

Time: 5 minutes
Teaching Skill: Coaching/Practice
Teacher’s Activity: The teacher writes another fraction subtraction problem (e.g., ⁷/₈ – ³/₈) on the board and guides pupils to solve it, asking them to identify numerators and denominators.
Pupils’ Activity: Pupils work through the example, stating the steps to arrive at the answer.
Learning Point: Pupils practice subtracting fractions with the same denominator.

Step 6: Further Practice/Application

Time: 5 minutes
Teaching Skill: Group Work/Problem Solving
Teacher’s Activity: The teacher provides a few more mixed practice problems for pupils to solve in pairs or small groups, circulating to offer support.
Pupils’ Activity: Pupils work together to solve the practice problems.
Learning Point: Pupils apply the learned concepts in varied problem settings.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Define regrouping in subtraction.
2. Subtract 456 from 891.
3. Calculate 700 – 349.
4. Subtract ⁴/₉ from ⁷/₉.
5. What do you do with the denominator when subtracting fractions with the same denominator?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 1 minute
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the main points of the lesson, emphasizing the importance of careful calculation and assigns homework involving a few subtraction problems for both 3-digit numbers with regrouping and fractions.
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and prepare for independent practice.

Home Task: Solve three new exercises on Subtraction. Show each step and check each answer.

Lesson Keywords

• Subtraction – The process of taking one number away from another.
• Regrouping – The process of exchanging values between place value columns in subtraction (also known as borrowing).
• Minuend – The number from which another number is subtracted.
• Subtrahend – The number to be subtracted from another number.
• Difference – The result obtained from subtracting one number from another.
• Numerator – The top number in a fraction, showing how many parts are being considered.
• Denominators – The bottom number in a fraction, showing the total number of equal parts in the whole.
• Fraction – A part of a whole.

Differentiation

For struggling learners, the teacher will provide additional one-on-one support, use more visual aids like manipulatives, and offer simpler practice problems. Advanced learners will be given more challenging problems, including those that require multiple steps or involve converting answers to simplest form for fractions.

Note for teachers using this lesson plan

Ensure that pupils have a solid grasp of place value before introducing 3-digit subtraction with regrouping. Use visual aids extensively for both topics to help pupils conceptualize the processes. Encourage pupils to explain their steps aloud to reinforce understanding.