Question:
Let \( * \) be a binary operation on \( \mathbb{N} \) defined by:
\[ a * b = \text{HCF}(a, b) \]
Find \( 22 * 4 \).
Solution:
Step 1: Apply definition
\[ 22 * 4 = \text{HCF}(22, 4) \]
Step 2: Find HCF
- Factors of 22: 1, 2, 11, 22
- Factors of 4: 1, 2, 4
Common factors: 1, 2 → Highest = 2
Final Answer:
\[ \boxed{2} \]