240. Приведите к наименьшему общему знаменателю дроби: 1) \(\frac{3}{8}\) и \(\frac{5}{12}\); 2) \(\frac{2}{15}\) и \(\frac{3}{10}\); 3) \(\frac{10}{17}\) и \(\frac{13}{34}\); 4) \(\frac{4}{13}\) и \(\frac{3}{4}\); 5) \(\frac{9}{14}\) и \(\frac{2}{21}\); 6) \(\frac{1}{20}\) и \(\frac{1}{30}\); 7) \(\frac{1}{9}, \frac{1}{4}\) и \(\frac{1}{6}\); 8) \(\frac{3}{28}, \frac{9}{14}\) и \(\frac{7}{8}\).

Наименьший общий знаменатель — наименьшее общее кратное знаменателей.

1. НОК(8, 12) = 24: \(\frac{3}{8}=\frac{9}{24}\), \(\frac{5}{12}=\frac{10}{24}\).
2. НОК(15, 10) = 30: \(\frac{2}{15}=\frac{4}{30}\), \(\frac{3}{10}=\frac{9}{30}\).
3. НОК(17, 34) = 34: \(\frac{10}{17}=\frac{20}{34}\), \(\frac{13}{34}=\frac{13}{34}\).
4. НОК(13, 4) = 52: \(\frac{4}{13}=\frac{16}{52}\), \(\frac{3}{4}=\frac{39}{52}\).
5. НОК(14, 21) = 42: \(\frac{9}{14}=\frac{27}{42}\), \(\frac{2}{21}=\frac{4}{42}\).
6. НОК(20, 30) = 60: \(\frac{1}{20}=\frac{3}{60}\), \(\frac{1}{30}=\frac{2}{60}\).
7. НОК(9, 4, 6) = 36: \(\frac{1}{9}=\frac{4}{36}\), \(\frac{1}{4}=\frac{9}{36}\), \(\frac{1}{6}=\frac{6}{36}\).
8. НОК(28, 14, 8) = 56: \(\frac{3}{28}=\frac{6}{56}\), \(\frac{9}{14}=\frac{36}{56}\), \(\frac{7}{8}=\frac{49}{56}\).