Grade 9 Mathematics Unit 2: The number system

This unit 2, “The Number System,” expands your understanding of numbers. You’ll move beyond whole numbers and integers to explore the full spectrum of rational and irrational numbers, which together form the real number system. You’ll learn how to classify, locate, and perform calculations with these different types of numbers.

---

Chapter 2.1 – Revision on Natural Numbers and Integers

This chapter quickly reviews the building blocks: Natural Numbers (the counting numbers 1, 2, 3…) and Integers (all whole numbers and their negatives …-2, -1, 0, 1, 2…).

---

Chapter 2.2 – Rational Numbers

Learn the formal definition of rational numbers as any number that can be expressed as a fraction. This section covers their properties, how to convert them between fractions and decimals, and how to locate them on a number line.

---

Chapter 2.3 – Irrational Numbers

Discover irrational numbers—numbers that cannot be expressed as a simple fraction. Their decimal representations are non-terminating and non-repeating. You’ll learn how to locate some of these numbers on a number line.

---

Chapter 2.4 – Real Numbers

This chapter unifies all the numbers you’ve studied. It defines the real number system as the set of all rational and irrational numbers combined. You’ll practice classifying real numbers as either rational or irrational.

---

Chapter 2.5 – Applications

Apply your new knowledge of the real number system to solve mathematical problems and practical, real-world situations that involve different types of numbers.

---

Learning Outcomes

By the end of this unit 2, you will be able to:

• Describe rational numbers.
• Locate rational numbers on a number line.
• Describe irrational numbers.
• Locate some irrational numbers on a number line.
• Define real numbers.
• Classify real numbers as rational and irrational.
• Solve mathematical problems involving real numbers.