0
Wiki User
4 over 21 is already in simplest form. The only factors of 4 are 1, 2, and 4; the only factors of 21 are 1, 3, 7, and 21. Since the only common factor is 1, we cannot simplify the fraction further.
4/21 is in its simplest form.
4/21
21/4
12/21 = 4/7 in its simplest form
12/21 = 4/7 in its simplest form.
21/4 is in its simplest form.
12/21 = 4/7
3/4
4/7