Question

What is the GCF of 16 and 21

Answer 1

The factors of  16  are  1,  2,  4,  8,  and  16 .

The factors of  21  are  1,  3,  7,  and  21 .

The common factors of  16  and  21  are      1 .

The greatest common factor of  16  and  21  is     1 . 

Answer 2

16 has the factors 1,2,4,8,16 and 21 has the factors 1,3,7,21

compare which numbers from 16 and 21 are similar and the greatest value... in this case 1

So, the greatest common factor of 16 and 21 in 1