Highest Common Factor (HCF)
The greatest number which is a common factor of two or more numbers is called their Highest Common Factors (HCF) or Greatest Common Divisor (GCD).
Example –
1) 35 = 1, 5, 7, 35
90 = 1, 2, 3, 5, 6, 9, 15, 18, 30, 45, 90
The common factors of 35 and 60 = 1, 5. Of these 5 is the greatest number.
So, the HCF of 35 and 90 is 5.
2) 72 = 1, 2, 3, 4, 6, 8, 9, 12, 18, 36, 72
112 = 1, 2, 4, 7, 8, 14, 16, 28, 56, 112
The common factors of 72 & 112 is = 1, 2, 4, 8. Of these 8 is the greatest number.
So, the HCF of 72 & 112 is 8.
Method Of Finding HCF –
There are two methods of finding the HCF of two or more numbers
1) By division method, 2) By Prime Factorization method