50. Найдите сумму:

50. Нахождение суммы: 1) 3 7/9 + 5 1/6 = 3 14/18 + 5 3/18 = 8 17/18 2) 8 7/16 + 3 3/10 = 8 35/80 + 3 24/80 = 11 59/80 3) 6 8/12 + 9 7/18 = 6 24/36 + 9 14/36 = 15 38/36 = 16 2/36 = 16 1/18 4) 9 3/16 + 4 7/12 + 3 5/24 = 9 18/96 + 4 56/96 + 3 20/96 = 16 94/96 = 16 47/48 51. Нахождение разности: 1) 8 3/7 - 4 2/5 = 8 15/35 - 4 14/35 = 4 1/35 2) 6 11/15 - 2 7/10 = 6 22/30 - 2 21/30 = 4 1/30 3) 16 17/18 - 2 11/12 = 16 34/36 - 2 33/36 = 14 1/36 4) 18 13/48 - 5 3/64 = 18 52/192 - 5 9/192 = 13 43/192 52. Выполнение вычитания: 1) 3 1/18 - 1/9 = 3 1/18 - 2/18 = 2 19/18 - 2/18 = 2 17/18 2) 3 17/27 - 2 13/18 = 3 34/54 - 2 39/54 = 2 88/54 - 2 39/54 = 49/54 3) 6 3/8 - 2 5/9 = 6 27/72 - 2 40/72 = 5 99/72 - 2 40/72 = 3 59/72 4) 8 11/42 - 5 43/126 = 8 33/126 - 5 43/126 = 7 159/126 - 5 43/126 = 2 116/126 = 2 58/63 5) 6 7/45 - 4 7/20 = 6 28/180 - 4 63/180 = 5 208/180 - 4 63/180 = 1 145/180 = 1 29/36 6) 9 1/21 - 5 16/63 = 9 3/63 - 5 16/63 = 8 66/63 - 5 16/63 = 3 50/63 53. Решение уравнений: 1) 8 3/4 - x = 3 5/16 x = 8 3/4 - 3 5/16 = 8 12/16 - 3 5/16 = 5 7/16 2) (x - 9 3/7) + 5 8/21 = 6 5/14 x - 9 3/7 = 6 5/14 - 5 8/21 = 6 15/42 - 5 16/42 = 5 57/42 - 5 16/42 = 41/42 x = 41/42 + 9 3/7 = 41/42 + 9 18/42 = 9 59/42 = 10 17/42 54. Скорость лодки: Скорость по течению = собств. скорость + скорость течения = 21 3/8 + 1 3/4 = 21 3/8 + 1 6/8 = 22 9/8 = 23 1/8 км/ч. Скорость против течения = собств. скорость - скорость течения = 21 3/8 - 1 3/4 = 21 3/8 - 1 6/8 = 20 11/8 - 1 6/8 = 19 5/8 км/ч. 55. Удобный способ: 1) (3/8 + 5/8) + (5/9 + 4/9) = 1 + 1 = 2 2) (4/15 + 11/15) + (3/7 + 6/7) = 15/15 + 9/7 = 1 + 1 2/7 = 2 2/7 3) (5 3/8 + 4 5/8) + (3 5/7 + 1 2/5) = 9 8/8 + (3 5/7 + 1 2/5) = 10 + 3 25/35 + 1 14/35 = 10 + 4 39/35 = 15 4/35