Advanced number types, including common factors, multiples, rational and irrational numbers, and reciprocals, play a pivotal role in the world of mathematics. This section aims to thoroughly explore these concepts, equipping students with the knowledge and techniques necessary to master them. We will delve into each type with detailed explanations and step-by-step examples.

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**Common Factors and Multiples**

**Definition and Identification**

**Common Factors**: Numbers that divide two or more numbers completely, leaving no remainder.- For instance, the common factors of 8 and 12 are 1, 2, and 4.

**Common Multiples**: Numbers that are multiples of two or more numbers.- The first few common multiples of 3 and 4 are 12, 24, and 36.

**Finding Common Factors and Multiples**

**Finding Common Factors**:- List the factors of each number.
- Identify the numbers that appear in both lists.

**Finding Common Multiples**:- List multiples of each number.
- Identify the numbers that appear in both lists.

**Rational and Irrational Numbers**

**Rational Numbers**

**Rational Numbers**are those that can be written as a fraction, where the numerator and denominator are integers, and the denominator is not zero.- Examples:$\dfrac{1}{2}$, -3, 0.75.

**Identifying Rational Numbers**: A number is rational if you can express it as a fraction.

**Irrational Numbers**

**Irrational Numbers**cannot be expressed as a fraction with integer numerators and denominators.- Examples: √2, π.

**Identifying Irrational Numbers**: Look for non-repeating, non-terminating decimal parts.

**Reciprocals**

**Understanding Reciprocals**

- A
**reciprocal**of a number is obtained by dividing 1 by that number.- For example, the reciprocal of 5 is $\dfrac{1}{5}$.

**Identifying Reciprocals**: To find the reciprocal of a fraction, invert it. For whole numbers, place them as the denominator with 1 as the numerator.

## Worked Examples

**Example 1: Identifying Common Factors**

**Question: **Find the common factors of 18 and 27.

**Solution:**

- Factors of 18: 1, 2, 3, 6, 9, 18.
- Factors of 27: 1, 3, 9, 27.
- Common Factors: Identify the factors that are the same in both lists - 1, 3, 9.

**Answer: **The common factors of 18 and 27 are 1, 3, and 9.

**Example 2: Identifying a Rational Number**

**Question: **Determine if 0.333... is rational.

**Solution:**

- 0.333... can be written as the fraction $\dfrac{1}{3}$.
- Since it can be expressed as a fraction, it is a rational number.

**Answer:** 0.333... is a **rational number** as it can be written as $\dfrac{1}{3}$.

**Example 3: Finding the Reciprocal**

**Question: **What is the reciprocal of $\dfrac{7}{4}$?

**Solution:**

- The reciprocal of a fraction is found by inverting the numerator and the denominator.
- For the fraction $\dfrac{7}{4}$, invert it to get $\dfrac{4}{7}.$

**Answer: **The reciprocal of $\dfrac{7}{4}$ is $\dfrac{4}{7}$.