Solutions by everydaycalculation.com

The GCF of 5 and 21 is 1.

- Find the prime factorization of 5

5 = 5 - Find the prime factorization of 21

21 = 3 × 7 - To find the GCF, multiply all the prime factors common to both numbers:

Therefore, GCF = 1

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Find hcf of: 10 & 42 15 & 63 25 & 105 35 & 147 10 & 21 5 & 42 15 & 21 5 & 63 25 & 21 5 & 105 35 & 21 5 & 147

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The greatest common factor (GCF) is also known as greatest common divisor (GCD) or highest common factor (HCF).

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