283. В 1/2 круга: 2/4, 3/6, 4/8, 5/10
284. В 1/3 круга: 2/6, 3/9, 4/12, 5/15
285. 1/2 = 3/6, 1/2 = 4/8, 1/3 = 2/6, 1/3 = 3/9, 1/4 = 2/8, 1/4 = 2/8, 1/4 = 3/12, 1/5 = 2/10, 1/5 = 3/15, 1/2 = 5/10, 1/2 = 6/12, 1/3 = 4/12, 1/3 = 5/15, 1/4 = 4/16, 1/4 = 5/20, 1/5 = 4/20, 1/5 = 5/25