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The highest common factor (HCF) of two whole numbers is the largest whole number which is a factor of both. HCF Example Consider the numbers 12 and 15: The factors of 12 are : 1, 2, 3, 4, 6, 12. The factors of 15 are : 1, 3, 5, 15. 1 and 3 are the only common factors (numbers which are factors of both 12 and 15). Therefore, the highest common factor of 12 and 15 is 3. The lowest common multiple (LCM) of two whole numbers is the smallest whole number which is a multiple of both. LCM Example Consider the numbers 12 and 15 again: The multiples of 12 are : 12, 24, 36, 48, 60, 72, 84, .... The multiples of 15 are : 15, 30, 45, 60, 75, 90, .... 60 is a common multiple (a multiple of both 12 and 15), and there are no lower common multiples. Therefore, the lowest common multiple of 12 and 15 is 60.
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HCF stands for Highest Common Factor i.e., it represents a unique no. among 2 or more numbers which is the only possible factor of highest value between them.
example: HCF of 8 and 12 is 4.

LCM stands for Lowest Common Factor i.e., it represents the no. which in terms of factors of 2 or more numbers posses the lowest value.
example: LCM of 8 and 12 is 24.

Relation between LCM and HCF of 2 numbers.
LCM * HCF = product of 2 numbers.