HCF = Highest Common Factor GCD = Greatest Common Divisor Example: Find HCF/GCD of 12 and 18 Method 1: List the factors Factors of 12: 1, 2, 3, 4, 6, 12 Factors of 18: 1, 2, 3, 6, 9, 18 Common factors: 1, 2, 3, 6 The highest common factor is 6 . So: HCF(12, 18) = GCD(12, 18) = 6 Euclidean algorithm For larger numbers, this is faster. Find GCD of 48 and 18 : 48 ÷ 18 = 2 remainder 12 18 ÷ 12 = 1 remainder 6 12 ÷ 6 = 2 remainder 0 When the remainder becomes 0 , the last non-zero remainder is the GCD. Answer = 6 For Decimal Numbers Example: HCF of 1.2 and 1.8 Step 1: Count decimal places Both numbers have 1 decimal place. Step 2: Multiply both by 10 1.2 × 10 = 12 1.8 × 10 = 18 Step 3: Find the HCF of 12 and 18 HCF = 6 Step 4: Divide by 10 6 ÷ 10 = 0.6 HCF of 1.2 and 1.8 = 0.6 Another example: 2.4 and 3.6 Multiply by 10: 2.4 → 24 3.6 → 36 HCF of 24 and 36 = 12 Divide by 10: 12 ÷ 10 = 1.2 So, HCF = 1.2 . If the numbers have different numbers of decimal...