Weight, Operations and Conversions in Kg and G for Primary 4

Class: Primary 4
Term: 2nd Term
Week: 7
Age: 9 years
Duration: 45 minutes
Subject: General Mathematics
Curriculum Theme: Measurement
Previous Lesson: Length, Addition, Subtraction and Word Problems.
Topic: WEIGHT
Subject Matter: Addition and subtraction of weights in kilograms and grams, multiplication and division of weights by whole numbers, quantitative reasoning on weight operations

Specific Objectives

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

Cognitive Domain:

• Solve problems involving addition of weights in kilograms and grams.
• Solve problems involving subtraction of weights in kilograms and grams.
• Perform multiplication of weights by whole numbers.
• Perform division of weights by whole numbers.
• Solve quantitative reasoning problems related to weight operations.

Affective Domain:

• Appreciate the importance of accurate weight measurement in daily life.
• Show interest in solving mathematical problems involving weight.

Psychomotor Domain:

• Accurately write down the steps and solutions for weight calculations.
• Demonstrate the ability to convert between kilograms and grams when solving problems.

Social Domain:

• Clearly communicate their understanding of weight operations.

Reference Materials

The following resources were used in planning this lesson:

• 9 Years Basic Education Curriculum (Primary 4 Mathematics)
• State Unified Scheme of Work (Primary 4 Mathematics)
• New General Mathematics for Primary Schools, Book 4

Instructional Materials

The teacher will teach this lesson with the aid of:

• Workbook and textbook (New General Mathematics for Primary Schools, Book 4)
• Chart showing units of weight and their conversions (1 kg = 1000g)
• Examples of objects with their weights labelled (e.g., a bag of sugar, a tin of milk)

Rationale for the Lesson

Understanding weight helps pupils measure objects in everyday life, such as food items or ingredients for cooking. This lesson enables them to perform basic calculations with weights, which is a practical skill for making informed decisions and managing quantities at home or in the market.

Prerequisite/Previous Knowledge

Pupils should have a basic understanding of what weight is, common units of measurement like kilograms and grams, and be proficient in basic arithmetic operations (addition, subtraction, multiplication, and division) with whole numbers.

Lesson Content/Board Summary

WEIGHT: Operations with Kilograms and Grams

Units of Weight

Weight is a measure of how heavy an object is. The standard units for measuring weight are kilograms (kg) and grams (g).

The relationship between kilograms and grams is:

• 1 kilogram (kg) = 1000 grams (g)

Addition of Weights

To add weights, arrange the numbers in columns for kilograms and grams. Add the grams first, then the kilograms. If the sum of grams is 1000 or more, convert it to kilograms and add to the kilogram column.

Example:

• Add 3 kg 450 g and 2 kg 700 g
• Solution:
• kg | g
• 3 | 450
• + 2 | 700
• ——-
• 5 | 1150
• Convert 1150 g to 1 kg 150 g.
• Add 1 kg to the kg column: 5 kg + 1 kg = 6 kg.
• Answer: 6 kg 150 g

Subtraction of Weights

To subtract weights, arrange the numbers in columns for kilograms and grams. Subtract the grams first, then the kilograms. If the grams to be subtracted are larger than the grams available, borrow 1 kg (which is 1000 g) from the kilogram column and add it to the gram column.

Example:

• Subtract 1 kg 800 g from 4 kg 200 g
• Solution:
• kg | g
• 3(4) | 1200(200) (Borrowed 1 kg = 1000 g)
• – 1 | 800
• ——-
• 2 | 400
• Answer: 2 kg 400 g

Multiplication of Weights by Whole Numbers

To multiply weights by a whole number, multiply the grams by the whole number first, then multiply the kilograms by the whole number. If the product of grams is 1000 or more, convert it to kilograms and add to the kilogram product.

Example:

• Multiply 2 kg 300 g by 3
• Solution:
• 300 g x 3 = 900 g
• 2 kg x 3 = 6 kg
• Answer: 6 kg 900 g

Division of Weights by Whole Numbers

To divide weights by a whole number, divide the kilograms first. If there is a remainder in kilograms, convert it to grams (by multiplying by 1000) and add it to the original grams. Then, divide the total grams by the whole number.

Example:

• Divide 5 kg 400 g by 2
• Solution:
• Divide kg: 5 kg ÷ 2 = 2 kg remainder 1 kg.
• Convert remainder to grams: 1 kg = 1000 g.
• Add to original grams: 1000 g + 400 g = 1400 g.
• Divide grams: 1400 g ÷ 2 = 700 g.
• Answer: 2 kg 700 g

Quantitative Reasoning on Weight Operations

Quantitative reasoning involves solving word problems that require one or more operations with weights. It tests the ability to understand the problem and apply the correct calculations.

Example:

• A bag of beans weighs 10 kg 500 g. If a family uses 1 kg 200 g each week, how much beans is left after 2 weeks?
• Solution:
• Amount used in 2 weeks = 1 kg 200 g x 2 = 2 kg 400 g.
• Beans left = 10 kg 500 g – 2 kg 400 g = 8 kg 100 g.
• Answer: 8 kg 100 g

Teaching Methods/Instructional Techniques

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

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to mention items they buy in the market that are measured by weight (e.g., rice, beans, sugar). The teacher then asks what units are used to measure these items.
Pupils’ Activity: Pupils respond by mentioning items and units like kilogram or gram.
Learning Point: Pupils recall prior knowledge of weight and its units, connecting it to real-life situations.

Step 2: Explanation of Weight Units and Conversion

Time: 5 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains what weight is and introduces the standard units: kilograms (kg) and grams (g), using a chart. The teacher emphasizes the conversion: 1 kg = 1000 g, and explains its importance in calculations.
Pupils’ Activity: Pupils listen attentively and note the units and conversion factor.
Learning Point: Pupils understand the basic units of weight and their relationship.

Step 3: Addition of Weights

Time: 8 minutes
Teaching Skill: Demonstration/Practice
Teacher’s Activity: The teacher demonstrates how to add weights in kilograms and grams on the board, explaining the column method and how to handle carrying over from grams to kilograms if the sum exceeds 1000 g. The teacher provides an example for pupils to solve.
Pupils’ Activity: Pupils observe the demonstration, ask questions, and solve the given example in their notebooks.
Learning Point: Pupils learn how to correctly add different weights.

Step 4: Subtraction of Weights

Time: 8 minutes
Teaching Skill: Demonstration/Practice
Teacher’s Activity: The teacher demonstrates how to subtract weights, emphasizing borrowing from the kilogram column when the grams to be subtracted are larger. The teacher gives another example for pupils to practice.
Pupils’ Activity: Pupils follow the demonstration and practice subtracting weights.
Learning Point: Pupils learn how to correctly subtract different weights, including borrowing.

Step 5: Multiplication and Division of Weights by Whole Numbers

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains and demonstrates how to multiply and divide weights by whole numbers, showing how to handle conversions during these operations. The teacher provides simple examples for both operations.
Pupils’ Activity: Pupils pay attention to the steps for multiplication and division and attempt the examples.
Learning Point: Pupils learn to multiply and divide weights by whole numbers.

Step 6: Quantitative Reasoning on Weight Operations

Time: 6 minutes
Teaching Skill: Problem Solving
Teacher’s Activity: The teacher presents a word problem involving weight operations and guides the pupils through the steps to solve it, emphasizing careful reading and identification of operations needed.
Pupils’ Activity: Pupils participate in solving the word problem and ask clarifying questions.
Learning Point: Pupils develop skills in applying weight operations to real-life problems.

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 weight.
2. State two common units for measuring weight.
3. Add 4 kg 350 g and 1 kg 800 g.
4. Subtract 2 kg 600 g from 7 kg 150 g.
5. Multiply 3 kg 120 g by 4.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of knowing how to perform operations with weights. The teacher assigns homework from the textbook.
Pupils’ Activity: Pupils listen to the summary and copy their homework.
Learning Point: Pupils consolidate their learning and prepare for independent practice.

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

Lesson Keywords

• Weight – A measure of how heavy an object is.
• Kilogram (kg) – A standard unit of weight, equal to 1000 grams.
• Gram (g) – A smaller unit of weight, where 1000 grams make 1 kilogram.
• Quantitative Reasoning – The ability to solve problems by applying numerical concepts and operations.

Differentiation

For struggling learners, the teacher will provide additional guided practice with simpler examples, focusing on one operation at a time and using visual aids like real objects. Advanced learners will be given more complex word problems and encouraged to create their own weight-related problems.

Note for teachers using this lesson plan

Ensure that pupils understand the concept of borrowing and carrying over between kilograms and grams, as this is a common area of difficulty. Use practical examples and encourage pupils to share their problem-solving strategies. Emphasize the importance of writing units correctly in all calculations.