Вычислите, применяя переместительное и сочетательное свойства сложения: 1) (2/35+3/28) + 1/28 = 2) (7/30+8/45) + (2/45+1/30) = 3) (5/24+11/60) + (13/60+1/24) =

1) (2/35 + 3/28) + 1/28 = 2/35 + (3/28 + 1/28) = 2/35 + (3 + 1) / 28 = 2/35 + 4/28 = 2/35 + 4 / (4 * 7) = 2/35 + 1/7 = 2/35 + (1 * 5) / (7 * 5) = 2/35 + 5/35 = (2 + 5) / 35 = 7/35 = 7 / (5 * 7) = 1/5 = 2/10 = 0,2;

2) (7/30 + 8/45) + (2/45 + 1/30) = (7/30 + 1/30) + (8/45 + 2/45) = 8/30 + 10/45 = 4/15 + 10/45 = 12/45 + 10/45 = 22/45;

3) (5/24 + 11/60) + (13/60 + 1/24) = (5/24 + 1/24) + (11/60 + 13/60) = 6/24 + 24/60 = 1/4 + 2/5 = 5/20 + 8/20 = 13/20 = 65/100 = 0,65.

Ответ: 1) 0,2; 2) 22/45; 3) 0,65.