Описание слайда: 1,2,3,4,5,6,7,8,9,10,11,12,13, 14,15,16,17,18,19,20 11,12,13,14,15,16,17,18,19,20,21, 22,23,24,25,26,27,28,29,30 20,21,22,23,24,25,26,27,28,29,30, 32,33,34,35,36,3738,39,40. :2 :3 :4 2 4 6 8 10 12 14 16 18 20 3 6 9 12 15 18 21 24 27 30 4 8 12 16 20 24 28 32 36 40