2. Вычислите: а) 2/5 * 3/7; б) 12/7 : 2/3; в) 11/10 : 5/1; г) 3/4 : 1/2; д) 25/4 : 5.

Решение:

1. \(\frac{2}{5} \cdot \frac{3}{7} = \frac{2 \cdot 3}{5 \cdot 7} = \frac{6}{35}\)
2. \(\frac{12}{7} \div \frac{2}{3} = \frac{12}{7} \cdot \frac{3}{2} = \frac{12 \cdot 3}{7 \cdot 2} = \frac{36}{14} = \frac{18}{7} = 2\frac{4}{7}\)
3. \(\frac{11}{10} \div 5 = \frac{11}{10} \cdot \frac{1}{5} = \frac{11 \cdot 1}{10 \cdot 5} = \frac{11}{50}\)
4. \(\frac{3}{4} \div \frac{1}{2} = \frac{3}{4} \cdot \frac{2}{1} = \frac{3 \cdot 2}{4 \cdot 1} = \frac{6}{4} = \frac{3}{2} = 1\frac{1}{2}\)
5. \(\frac{25}{4} \div 5 = \frac{25}{4} \cdot \frac{1}{5} = \frac{25 \cdot 1}{4 \cdot 5} = \frac{25}{20} = \frac{5}{4} = 1\frac{1}{4}\)

Ответ: а) \(\frac{6}{35}\); б) \(2\frac{4}{7}\); в) \(\frac{11}{50}\); г) \(1\frac{1}{2}\); д) \(1\frac{1}{4}\).