Lesson 1: Operations on Whole Numbers

📚 Introduction

Welcome to Lesson 1! Have you ever needed to quickly calculate how much money you need to buy snacks or how many seats are left on a bus? 🤔

Those everyday activities use whole numbers — numbers without fractions or decimals. Learning how to add, subtract, multiply, and divide whole numbers correctly makes life a lot easier!

Today, we will break down these operations in a fun and simple way, with examples and real-life tips. Ready? Let’s go! 🚀

🧠 Key Concepts and Explanations

1. What Are Whole Numbers?

Whole numbers are numbers like 0, 1, 2, 3, 10, 250 — numbers without fractions or decimal parts. They’re positive or zero!

2. Addition of Whole Numbers ➕

Addition means joining two or more numbers together to find a total.

Formula:

Example: What is 387 + 459?

• Add the units: 7 + 9 = 16 (write 6, carry 1)
• Add the tens: 8 + 5 + 1 = 14 (write 4, carry 1)
• Add the hundreds: 3 + 4 + 1 = 8

Answer: 846 ✅

3. Subtraction of Whole Numbers ➖

Subtraction means finding the difference between two numbers.

Formula:

Example: What is 725 – 468?

• Borrow where needed!
• 5 – 8: borrow from tens → 15 – 8 = 7
• 1 – 6: borrow again → 11 – 6 = 5
• 6 – 4 = 2

Answer: 257 ✅

4. Multiplication of Whole Numbers ✖️

Multiplication means repeated addition.

Formula:

Example: Find 64 × 5.

• 4 × 5 = 20 (write 0, carry 2)
• 6 × 5 = 30 + 2 = 32

Answer: 320 ✅

5. Division of Whole Numbers ➗

Division means splitting into equal groups.

Formula:

Example: Find 816 ÷ 8.

• 8 into 8 = 1
• 8 into 1 = 0 (carry the 1 to the next digit)
• 8 into 16 = 2

Answer: 102 ✅

📈 Useful Tables

📝 Practice Exercises

A. Quick Computations

1. 267 + 489 = ______
2. 915 – 478 = ______
3. 37 × 8 = ______
4. 720 ÷ 9 = ______

B. Real-Life Word Problems

1. A class has 215 boys and 193 girls. How many students are there in total?
2. A tailor had 485 metres of fabric and sold 168 metres. How much is left?
3. A farmer packs 48 oranges in one box. How many oranges in 25 boxes?
4. A school has 960 students divided equally into 8 classes. How many students per class?

C. Fill in the Blanks

• 375 + ___ = 800
• ___ – 145 = 355
• 18 × ___ = 360
• ___ ÷ 6 = 20

✅ Answers and Explanations

Quick Computations

1. 756
2. 437
3. 296
4. 80

Real-Life Word Problems

1. 215 + 193 = 408 students
2. 485 – 168 = 317 metres
3. 48 × 25 = 1200 oranges
4. 960 ÷ 8 = 120 students

Fill in the Blanks

• 425
• 500
• 20
• 120

🔄 Recap

Today you learned that whole numbers can be added, subtracted, multiplied, and divided. These basic skills are the foundation for all other mathematics! 🧠

💬 Reflection

Think about this: How would you use addition, subtraction, multiplication, or division if you were planning a birthday party for 30 friends? 🎂