The HCF of two or more numbers is the largest number that is a factor of all the given numbers. For example, to find the HCF of 12 and 18:
• Factors of 12: 1, 2, 3, 4, 6, 12
• Factors of 18: 1, 2, 3, 6, 9, 18
• Common factors: 1, 2, 3, 6
• HCF: 6 (the largest common factor)