№1. Вычислите: 1) \(\frac{2}{5} + \frac{3}{10}\) 2) \(\frac{12}{20} - \frac{7}{30}\) 3) \(\frac{7}{8} + \frac{5}{6} - \frac{5}{24}\) 4) \(\frac{15}{16} - \frac{15}{32} + \frac{51}{64}\)

Ответ: 1) 0,7; 2) 0,233; 3) 1,458; 4) 2,422

Решаем:

1. \(\frac{2}{5} + \frac{3}{10} = \frac{2 \cdot 2}{5 \cdot 2} + \frac{3}{10} = \frac{4}{10} + \frac{3}{10} = \frac{7}{10} = 0,7\)
2. \(\frac{12}{20} - \frac{7}{30} = \frac{12 \cdot 3}{20 \cdot 3} - \frac{7 \cdot 2}{30 \cdot 2} = \frac{36}{60} - \frac{14}{60} = \frac{22}{60} = \frac{11}{30} = 0,233\)
3. \(\frac{7}{8} + \frac{5}{6} - \frac{5}{24} = \frac{7 \cdot 3}{8 \cdot 3} + \frac{5 \cdot 4}{6 \cdot 4} - \frac{5}{24} = \frac{21}{24} + \frac{20}{24} - \frac{5}{24} = \frac{36}{24} = \frac{3}{2} = 1,5\)
4. \(\frac{15}{16} - \frac{15}{32} + \frac{51}{64} = \frac{15 \cdot 4}{16 \cdot 4} - \frac{15 \cdot 2}{32 \cdot 2} + \frac{51}{64} = \frac{60}{64} - \frac{30}{64} + \frac{51}{64} = \frac{81}{64} = 1,266\)

Ответ: 1) 0,7; 2) 0,233; 3) 1,458; 4) 2,422