The HCF of two numbers is the Highest Common Factor of the numbers. Factors of a given number are numbers which divide the number in question with a remainder of zero. The Highest Common Factor is the largest number that divides two numbers such that the result of each division operation has a remainder of zero. In practice, if an HCF exists for two numbers, generally speaking the HCF is either equal to the smaller of the two numbers or the two numbers are equal and so it is either of the them.
Things You'll Need
 Two numbers
Find the HCF

Identify which of the two numbers is larger. Note that they may be equal.

Divide the larger number by the smaller number.

Take the divisor and divide it by the remainder.

Repeat the process of dividing the divisor from the previous operation by the remainder until the remainder is equal to 0.
References
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