3,216 = 3 + 0,216 = 3 + 216/1000 = 3 + 54/250 = (3*250 + 54) / 250 = 804/250
3,21(6) = 3 + 0,21(6) = 3 + 21(6)/990 = 3 + 216/990 = (3*330 + 216) / 990 = 996/990 = 332/330
3,216 = 3 + 0,216 = 3 + 216/1000 = 3 + 54/250 = (3*250 + 54) / 250 = 804/250
3,21(6) = 3 + 0,21(6) = 3 + 21(6)/990 = 3 + 216/990 = (3*330 + 216) / 990 = 996/990 = 332/330