Set Operations

The union of two sets $A$ and $B$, denoted as $A \cup B$ (

$A \cup B$

) is the set containing all elements from $A$ or $B$ (or both): $A \cup B = \;$$\{ x \mid x \in A \,$$\text{ or } x \in B \}$. Examples:

• If $A = \{1,2,3\}$ and $B = \{3,4,5\}$, then $A \cup B = \{1,2,3,4,5\}$.
• If $A = \{x, y\}$ and $B = \{y, z\}$, then $A \cup B = \{x, y, z\}$.
• If $A = \{1,2\}$ and $B = \{3,4\}$, then $A \cup B = \{1,2,3,4\}$.

---

Fun Class Activities:

1. Let $A = \{1, 3, 5, 7, 9\}$ and $B = \{2, 3, 6, 7, 10\}$. Find $A \cap B$ and $A \cup B$
2. Given the sets $X = \{a, b, c, d\}$ and $Y = \{c, d, e, f\}$, find $X \cap Y$ and $X \cup Y$.
3. Let $P = \{10, 20, 30, 40\}$ and $Q = \{30, 40, 50, 60\}$. Compute $P \cap Q$ and $P \cup Q$.