Question

Find the greatest common factor of
7, 15 and 21

Answer 1

Answer:

GCF = 1

for the values 15, 17, 21

Solution by Factorization:

The factors of 15 are: 1, 3, 5, 15

The factors of 17 are: 1, 17

The factors of 21 are: 1, 3, 7, 21

Then the greatest common factor is 1.

Answer 2

7 is prime.
but
3 factors into 15 and 21
but
7 factors into 21