Приведите дроби к наименьшему общему знаменателю: a) 1/2 и 1/3 ; б) 2/5 и 3/4 ; в) 5/6 и 5/7 ; г) 9/10 и 2/9 ; 3/8 и 2/5 ; 8/9 и 3/5 ; 7/15 и 3/8 ; 5/4 и 5/6 . 1/6 и 5/9 . 3/10 и 8/15 . 3/8 и 5/12 .

a) $$\frac{1}{2} = \frac{1 \cdot 3}{2 \cdot 3} = \frac{3}{6}$$, $$\frac{1}{3} = \frac{1 \cdot 2}{3 \cdot 2} = \frac{2}{6}$$

б) $$\frac{2}{5} = \frac{2 \cdot 4}{5 \cdot 4} = \frac{8}{20}$$, $$\frac{3}{4} = \frac{3 \cdot 5}{4 \cdot 5} = \frac{15}{20}$$

в) $$\frac{5}{6} = \frac{5 \cdot 7}{6 \cdot 7} = \frac{35}{42}$$, $$\frac{5}{7} = \frac{5 \cdot 6}{7 \cdot 6} = \frac{30}{42}$$

г) $$\frac{9}{10} = \frac{9 \cdot 9}{10 \cdot 9} = \frac{81}{90}$$, $$\frac{2}{9} = \frac{2 \cdot 10}{9 \cdot 10} = \frac{20}{90}$$

$$\frac{3}{8} = \frac{3 \cdot 5}{8 \cdot 5} = \frac{15}{40}$$, $$\frac{2}{5} = \frac{2 \cdot 8}{5 \cdot 8} = \frac{16}{40}$$

$$\frac{8}{9} = \frac{8 \cdot 5}{9 \cdot 5} = \frac{40}{45}$$, $$\frac{3}{5} = \frac{3 \cdot 9}{5 \cdot 9} = \frac{27}{45}$$

$$\frac{7}{15} = \frac{7 \cdot 8}{15 \cdot 8} = \frac{56}{120}$$, $$\frac{3}{8} = \frac{3 \cdot 15}{8 \cdot 15} = \frac{45}{120}$$

$$\frac{5}{4} = \frac{5 \cdot 3}{4 \cdot 3} = \frac{15}{12}$$, $$\frac{5}{6} = \frac{5 \cdot 2}{6 \cdot 2} = \frac{10}{12}$$

$$\frac{1}{6} = \frac{1 \cdot 3}{6 \cdot 3} = \frac{3}{18}$$, $$\frac{5}{9} = \frac{5 \cdot 2}{9 \cdot 2} = \frac{10}{18}$$

$$\frac{3}{10} = \frac{3 \cdot 3}{10 \cdot 3} = \frac{9}{30}$$, $$\frac{8}{15} = \frac{8 \cdot 2}{15 \cdot 2} = \frac{16}{30}$$

$$\frac{3}{8} = \frac{3 \cdot 3}{8 \cdot 3} = \frac{9}{24}$$, $$\frac{5}{12} = \frac{5 \cdot 2}{12 \cdot 2} = \frac{10}{24}$$

Ответ: a) 3/6 и 2/6; б) 8/20 и 15/20; в) 35/42 и 30/42; г) 81/90 и 20/90; 15/40 и 16/40; 40/45 и 27/45; 56/120 и 45/120; 15/12 и 10/12; 3/18 и 10/18; 9/30 и 16/30; 9/24 и 10/24