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

Решение:

1. \[25 + \frac{15}{4} = \frac{25 \cdot 4}{4} + \frac{15}{4} = \frac{100+15}{4} = \frac{115}{4} = 28.75\]
2. \[\frac{3}{2} - \frac{9}{5} = \frac{3 \cdot 5}{10} - \frac{9 \cdot 2}{10} = \frac{15-18}{10} = \frac{-3}{10} = -0.3\]
3. \[\left(\frac{19}{8} + \frac{11}{12}\right) \cdot \frac{5}{48} = \left(\frac{19 \cdot 3}{24} + \frac{11 \cdot 2}{24}\right) \cdot \frac{5}{48} = \left(\frac{57+22}{24}\right) \cdot \frac{5}{48} = \frac{79}{24} \cdot \frac{5}{48} = \frac{79 \cdot 5}{24 \cdot 48} = \frac{395}{1152}\]

Ответ: 1) 28.75; 2) -0.3; 3) 395/1152