一、口算。
$\frac {1}{3}×66=$
$\frac {1}{2}×\frac {5}{8}=$
$22×\frac {5}{11}=$
$26×\frac {10}{13}=$
$\frac {9}{11}+\frac {1}{33}=$
$\frac {1}{3}×\frac {1}{3}=$
$\frac {5}{7}-\frac {1}{2}=$
$0.125×\frac {4}{9}=$
$\frac {3}{4}×\frac {3}{8}=$
$\frac {2}{3}-\frac {1}{4}=$
$5×\frac {5}{7}=$
$\frac {1}{21}×\frac {7}{2}=$
$\frac {2}{3}×2=$
$\frac {17}{10}-\frac {4}{5}=$
$\frac {3}{4}+\frac {1}{5}=$
$12×\frac {3}{8}=$
$\frac {4}{5}×\frac {3}{2}=$
$\frac {3}{7}×\frac {3}{5}=$
$\frac {6}{7}+\frac {2}{21}=$
$\frac {2}{5}×\frac {1}{2}=$
$\frac {5}{16}×\frac {8}{15}=$

22 $\frac{5}{16}$ 10 20 $\frac{28}{33}$ $\frac{1}{9}$ $\frac{3}{14}$ $\frac{1}{18}$ $\frac{9}{32}$ $\frac{5}{12}$ $\frac{25}{7}$ $\frac{1}{6}$ $\frac{4}{3}$ $\frac{9}{10}$ $\frac{19}{20}$ $\frac{9}{2}$ $\frac{6}{5}$ $\frac{9}{35}$ $\frac{20}{21}$ $\frac{1}{5}$ $\frac{1}{6}$

$\frac{1}{3}×66=22$
$\frac{1}{2}×\frac{5}{8}=\frac{5}{16}$
$22×\frac{5}{11}=10$
$26×\frac{10}{13}=20$
$\frac{9}{11}+\frac{1}{33}=\frac{28}{33}$
$\frac{1}{3}×\frac{1}{3}=\frac{1}{9}$
$\frac{5}{7}-\frac{1}{2}=\frac{3}{14}$
$0.125×\frac{4}{9}=\frac{1}{18}$
$\frac{3}{4}×\frac{3}{8}=\frac{9}{32}$
$\frac{2}{3}-\frac{1}{4}=\frac{5}{12}$
$5×\frac{5}{7}=\frac{25}{7}$
$\frac{1}{21}×\frac{7}{2}=\frac{1}{6}$
$\frac{2}{3}×2=\frac{4}{3}$
$\frac{17}{10}-\frac{4}{5}=\frac{9}{10}$
$\frac{3}{4}+\frac{1}{5}=\frac{19}{20}$
$12×\frac{3}{8}=\frac{9}{2}$
$\frac{4}{5}×\frac{3}{2}=\frac{6}{5}$
$\frac{3}{7}×\frac{3}{5}=\frac{9}{35}$
$\frac{6}{7}+\frac{2}{21}=\frac{20}{21}$
$\frac{2}{5}×\frac{1}{2}=\frac{1}{5}$
$\frac{5}{16}×\frac{8}{15}=\frac{1}{6}$

二、计算下面各题。
$\frac {5}{7}×12×\frac {7}{5}$
$\frac {1}{3}×\frac {13}{18}×\frac {10}{13}$
$\frac {2}{5}×\frac {2}{7}×\frac {7}{11}$
$16×\frac {9}{8}×\frac {5}{9}$
$\frac {2}{3}×\frac {1}{6}×\frac {1}{2}$
$\frac {10}{9}×\frac {7}{15}×\frac {12}{35}$

12 $\frac{5}{27}$ $\frac{4}{55}$ 10 $\frac{1}{18}$ $\frac{8}{45}$

$\frac{5}{7}×12×\frac{7}{5}$
$=\frac{5}{7}×\frac{7}{5}×12$
$=1×12$
$=12$
$\frac{1}{3}×\frac{13}{18}×\frac{10}{13}$
$=\frac{1}{3}×(\frac{13}{18}×\frac{10}{13})$
$=\frac{1}{3}×\frac{10}{18}$
$=\frac{1}{3}×\frac{5}{9}$
$=\frac{5}{27}$
$\frac{2}{5}×\frac{2}{7}×\frac{7}{11}$
$=\frac{2}{5}×(\frac{2}{7}×\frac{7}{11})$
$=\frac{2}{5}×\frac{2}{11}$
$=\frac{4}{55}$
$16×\frac{9}{8}×\frac{5}{9}$
$=16×(\frac{9}{8}×\frac{5}{9})$
$=16×\frac{5}{8}$
$=2×5$
$=10$
$\frac{2}{3}×\frac{1}{6}×\frac{1}{2}$
$=\frac{2×1×1}{3×6×2}$
$=\frac{2}{36}$
$=\frac{1}{18}$
$\frac{10}{9}×\frac{7}{15}×\frac{12}{35}$
$=\frac{10×7×12}{9×15×35}$
$=\frac{840}{4725}$
$=\frac{8}{45}$