27. 1) Вычисли значения выражений: 45 + 27 : 3 − 12; 90 − 36 : 3 ⋅ 2; 84 : 4 ⋅ 3 : 2; 100 − 10 ⋅ 9 − 8; 17 + 15 ⋅ 3 ⋅ 0; 5 ⋅ 5 + 75 : 5; 17 ⋅ 3 + 2 ⋅ 10; 80 − 5 ⋅ 2 : 10; 72 : 6 + 6 ⋅ 5. 2) Измени порядок действий с помощью скобок и вычисли значения полученных выражений.

Сначала выполняем умножение и деление, затем сложение и вычитание.

1. 45 + 27 : 3 − 12 = 45 + 9 − 12 = 42.
2. 90 − 36 : 3 ⋅ 2 = 90 − 12 ⋅ 2 = 66.
3. 84 : 4 ⋅ 3 : 2 = 21 ⋅ 3 : 2 = 31.5.
4. 100 − 10 ⋅ 9 − 8 = 100 − 90 − 8 = 2.
5. 17 + 15 ⋅ 3 ⋅ 0 = 17 + 45 ⋅ 0 = 17.
6. 5 ⋅ 5 + 75 : 5 = 25 + 15 = 40.
7. 17 ⋅ 3 + 2 ⋅ 10 = 51 + 20 = 71.
8. 80 − 5 ⋅ 2 : 10 = 80 − 10 : 10 = 79.
9. 72 : 6 + 6 ⋅ 5 = 12 + 30 = 42.

Примеры изменения порядка действий скобками:

1. (45 + 27) : 3 − 12 = 72 : 3 − 12 = 12.
2. (90 − 36) : 3 ⋅ 2 = 54 : 3 ⋅ 2 = 36.
3. 84 : (4 ⋅ 3) : 2 = 84 : 12 : 2 = 3.5.
4. (100 − 10) ⋅ 9 − 8 = 90 ⋅ 9 − 8 = 802.
5. (17 + 15) ⋅ 3 ⋅ 0 = 32 ⋅ 3 ⋅ 0 = 0.
6. (5 ⋅ 5 + 75) : 5 = 100 : 5 = 20.
7. 17 ⋅ (3 + 2) ⋅ 10 = 17 ⋅ 5 ⋅ 10 = 850.
8. (80 − 5) ⋅ 2 : 10 = 75 ⋅ 2 : 10 = 15.
9. (72 : 6 + 6) ⋅ 5 = (12 + 6) ⋅ 5 = 90.

Ответ: значения первой части — 42; 66; 31.5; 2; 17; 40; 71; 79; 42.