Find the GCF of 21, 63 and 105.

21

Step-by-step explanation:

GCF of 21, 63 and 105

Break these numbers into prime factors

21 = 3*7

63 = 9*7 = 3*3*7

105 = 15*7 = 3*5*7

There is a 3, 7 in all the terms

The largest number of 3's in the terms is 1

The largest number of 7's is 1

Multiply the largest number of terms together

3*7 = 21

21

Step-by-step explanation:

To find the greatest common factor between a set of numbers, you can list the factors of those numbers and find the largest one they each have in common.

A factor of a number is a number which can be multiplied against another number to get your original number.

Factors of 21: 1, 3, 7, 21

Factors of 63: 1, 3, 7, 9, 21, 63

Factors of 105: 1, 3, 5, 7, 15, 21, 35, 105

21 is the greatest factor which all three have in common.