№3 Вычислите: 1) 4/25 + 15/4 = 2) 3/2 - 9/5 = 3) (19/8 + 11/12) : 5/48 =

Решение:

1. $$ \frac{4}{25} + \frac{15}{4} = \frac{4 \times 4 + 15 \times 25}{100} = \frac{16 + 375}{100} = \frac{391}{100} = 3.91 $$

2. $$ \frac{3}{2} - \frac{9}{5} = \frac{3 \times 5 - 9 \times 2}{10} = \frac{15 - 18}{10} = \frac{-3}{10} = -0.3 $$

3. $$ \left( \frac{19}{8} + \frac{11}{12} \right) : \frac{5}{48} = \left( \frac{19 \times 3 + 11 \times 2}{24} \right) : \frac{5}{48} = \left( \frac{57 + 22}{24} \right) : \frac{5}{48} = \frac{79}{24} \times \frac{48}{5} = \frac{79 \times 2}{5} = \frac{158}{5} = 31.6 $$

Ответ: 1) 3.91; 2) -0.3; 3) 31.6