Subtraction (1–100) — Understanding Minus, Minuend, and Subtrahend – Primary 1 Basic Science Lesson Note

TOPIC: Math Facts – Subtraction (1–100)
SUBTOPIC: Counting Numbers 81–100, Meaning of Subtraction, Minuend and Subtrahend, Subtracting within 10, and Real-Life Application of Subtraction
CLASS: Primary 1
DATE: ____________________
PERIOD: ____________________
DURATION: 40 minutes

LEARNING OBJECTIVES

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

1. Count and identify numbers from 81 to 100 correctly.
2. Explain the meaning of subtraction and the subtraction sign (−).
3. Identify the minuend and subtrahend in subtraction.
4. Subtract numbers correctly within 10.
5. Apply subtraction in real-life situations.

KEY VOCABULARY WORDS

Subtract, Minus (−), Equal (=), Take away, Left, Difference, Minuend, Subtrahend, Count, Numbers.

INSTRUCTIONAL MATERIALS

• Number chart (1–100)
• Flashcards showing subtraction facts (1–10)
• Counters, sticks, or bottle tops
• Subtraction chart
• Real-life objects (e.g., fruits, pencils, toys)
• Whiteboard and marker

INTRODUCTORY ACTIVITY

1. Begin by counting numbers 81 to 100 aloud with pupils.
2. Ask: “If I have 5 sweets and eat 2, how many are left?”
3. Pupils respond. The teacher introduces the word ‘subtraction’ and explains that it means taking away or removing some objects.

CONTENT OF THE LESSON

1. Counting Numbers (81–100)

Let’s continue counting numbers from 81 to 100:

81, 82, 83, 84, 85, 86, 87, 88, 89, 90,

91, 92, 93, 94, 95, 96, 97, 98, 99, 100

🧮 Diagram: Number Chart (81–100)

2. Meaning of Subtraction

Subtraction means taking away or removing some objects from a group.
It helps us find how many are left or the difference between two numbers.

We use the minus sign (−) for subtraction.

Example 1:
5 − 2 = 3 → “Five minus two equals three.”

Example 2 (using objects):

So, 5 − 2 = 3

🧩 Diagram: Subtraction Illustration

3. Identifying Minuend and Subtrahend

In subtraction:

• The Minuend is the number you start with.
• The Subtrahend is the number you take away.
• The Difference is the answer (what is left).

Example:
7 − 3 = 4
Here,

• 7 → Minuend
• 3 → Subtrahend
• 4 → Difference

4. Subtraction within 10

Let’s practice simple subtractions:

Remember: Always start from the bigger number when subtracting.

5. Real-Life Application of Subtraction

Subtraction happens every day.
Examples:

• You have 5 pencils, give 2 to your friend. How many left? → 3 pencils.
• There are 10 mangoes on a tree. 4 fall down. How many remain? → 6 mangoes.
• 8 birds were on a tree, 3 flew away. 8 − 3 = 5 birds left.

🖼️ Diagram: Real-Life Subtraction Example (Birds on a Tree)

CLASS EXERCISE 1

1. Write the numbers from 81 to 100.
2. Fill in the missing numbers: 81, ___, 83, ___, 85, ___, 87, ___, 89, ___
3. Subtract:
   a. 6 − 2 = ______
   b. 9 − 3 = ______
   c. 10 − 5 = ______
4. What is the difference between 8 and 4? ______
5. In 7 − 3 = 4, what is the minuend? ______

CLASS EXERCISE 2

1. There are 8 oranges. 3 are eaten. How many are left?
2. 9 birds were on a tree. 4 flew away. How many remained?
3. If you have 10 sweets and give 5 to your friend, how many sweets do you have now?
4. Fill in the blank: 5 − ___ = 2
5. Draw 6 apples and cross out 2. How many are left?

CLASS EXERCISE 3 (For Fast Learners)

ASSIGNMENT (Multiple-Choice Questions)

(Write answers in your exercise book)

1. Subtraction means ______ (a) adding together (b) taking away (c) counting up (d) none
2. The sign used for subtraction is ______ (a) + (b) ÷ (c) − (d) =
3. In 9 − 3 = 6, the number 9 is called the ______ (a) subtrahend (b) difference (c) minuend (d) number line
4. 7 − 4 = ______ (a) 2 (b) 4 (c) 3 (d) 5

There are 8 mangoes, 3 are eaten. How many left? (a) 4 (b) 5 (c) 6 (d) 7