Question

What is a common denominator of 1/2 and 1/4

Answer 1

If you're trying to rewrite 1/2 and 1/4 in terms of the same common denominator, all you have to do is multiply the top and bottom of 1/2 by 4 (which is the denominator of 1/4) and the top and bottom of 1/4 by 2 (which is the denominator of 1/2) to find that 1/2 = (1 x 4) / (2 x 4) = 4/8 and 1/6 = (1 x 2) / (4 x 2) = 2/8.

Answer 2

If you need to work with 1/2 and 1/4 both with the same denominator,
then the easiest one to use is '4'.  The 1/2 is the same thing as  2/4.