Решение задания 60

1) $$4 \cdot \frac{4}{21} = \frac{4 \cdot 4}{21} = \frac{16}{21}$$

2) $$6 \cdot \frac{7}{18} = \frac{6 \cdot 7}{18} = \frac{42}{18} = \frac{7}{3} = 2 \frac{1}{3}$$

3) $$\frac{5}{14} \cdot 28 = \frac{5 \cdot 28}{14} = \frac{5 \cdot 2}{1} = 10$$

4) $$5 \frac{3}{5} \cdot \frac{3}{7} = \frac{5 \cdot 5 + 3}{5} \cdot \frac{3}{7} = \frac{28}{5} \cdot \frac{3}{7} = \frac{4 \cdot 3}{5} = \frac{12}{5} = 2 \frac{2}{5}$$

5) $$2 \frac{2}{15} \cdot 1 \frac{9}{16} = \frac{2 \cdot 15 + 2}{15} \cdot \frac{1 \cdot 16 + 9}{16} = \frac{32}{15} \cdot \frac{25}{16} = \frac{2 \cdot 5}{3} = \frac{10}{3} = 3 \frac{1}{3}$$

6) $$1 \frac{7}{8} \cdot 1 \frac{1}{15} \cdot 1 \frac{7}{16} = \frac{1 \cdot 8 + 7}{8} \cdot \frac{1 \cdot 15 + 1}{15} \cdot \frac{1 \cdot 16 + 7}{16} = \frac{15}{8} \cdot \frac{16}{15} \cdot \frac{23}{16} = \frac{23}{8} = 2 \frac{7}{8}$$