Question

What is i hcf of 21 and 28

Answer 1

$21|3 \\ 7 \ |7 \\ 1 \\\\ 21=3*7 \\\\ 28|2 \\ 14|2 \\ 7 \ |7 \\ 1 \\\\ 28=2^2*7 \\\\ H.C.F(21;28)\to\boxed{7}$

Answer 2

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

The factors of  28  are  1,  2,  4,  7,  14, and  28 .

The factors common to both numbers are  1  and  7 .

The greatest one is  7.