Неделя 1, Задание 6: Вычислите.

Решение:

1. \( 18 \cdot \left(\frac{1}{9}\right)^2 - 20 \cdot \frac{1}{9} = 18 \cdot \frac{1}{81} - \frac{20}{9} = \frac{18}{81} - \frac{20}{9} = \frac{2}{9} - \frac{20}{9} = -\frac{18}{9} = -2 \)
2. \( \left(\frac{19}{8} + \frac{11}{12}\right) \cdot 5 : \frac{5}{48} = \left(\frac{19 \cdot 3 + 11 \cdot 2}{24}\right) \cdot 5 \cdot \frac{48}{5} = \left(\frac{57 + 22}{24}\right) \cdot 48 = \frac{79}{24} \cdot 48 = 79 \cdot 2 = 158 \)
3. \( \left(2\frac{3}{4} + 2\frac{1}{5}\right) \cdot 16 = \left(\frac{11}{4} + \frac{11}{5}\right) \cdot 16 = \left(\frac{11 \cdot 5 + 11 \cdot 4}{20}\right) \cdot 16 = \left(\frac{55 + 44}{20}\right) \cdot 16 = \frac{99}{20} \cdot 16 = \frac{99 \cdot 4}{5} = \frac{396}{5} = 79,2 \)

Ответ: 1) -2; 2) 158; 3) 79,2.