一、口算。
$\frac {13}{8}×\frac {4}{39}=$
$\frac {5}{3}×\frac {3}{5}=$
$\frac {2}{3}×\frac {7}{2}=$
$\frac {5}{8}+\frac {1}{4}=$
$\frac {11}{5}×\frac {10}{11}=$
$\frac {3}{8}+\frac {7}{2}=$
$1-\frac {5}{7}=$
$\frac {3}{4}×\frac {5}{6}=$
$60×\frac {4}{15}=$
$\frac {2}{3}+\frac {3}{2}=$
$\frac {8}{7}×0.125=$
$\frac {9}{2}×\frac {2}{3}=$
$28×\frac {2}{21}=$
$\frac {8}{5}×\frac {8}{5}=$
$\frac {2}{3}-\frac {1}{2}=$
$\frac {16}{25}×\frac {5}{24}=$
$\frac {11}{2}+\frac {5}{4}=$
$\frac {7}{6}×\frac {3}{5}=$
$\frac {5}{6}-\frac {7}{20}=$
$\frac {2}{21}×\frac {7}{4}=$
$\frac {4}{3}×\frac {15}{16}=$

$\frac{1}{6}$ 1 $\frac{7}{3}$ $\frac{7}{8}$ 2 $\frac{31}{8}$ $\frac{2}{7}$ $\frac{5}{8}$ 16 $\frac{13}{6}$ $\frac{1}{7}$ 3 $\frac{8}{3}$ $\frac{64}{25}$ $\frac{1}{6}$ $\frac{2}{15}$ $\frac{27}{4}$ $\frac{7}{10}$ $\frac{29}{60}$ $\frac{1}{6}$ $\frac{5}{4}$

二、计算下面各题。
$\frac {9}{10}×\frac {4}{5}×3$
$\frac {3}{10}×\frac {5}{6}×\frac {3}{5}$
$\frac {1}{5}×\frac {10}{39}×\frac {13}{8}$
$\frac {4}{9}×36×\frac {5}{8}$
$\frac {15}{16}×\frac {4}{25}×\frac {20}{3}$
$\frac {10}{51}×\frac {6}{7}×\frac {34}{25}$

$\frac{54}{25}$ $\frac{3}{20}$ $\frac{1}{12}$ 10 1 $\frac{8}{35}$

$\frac{9}{10}×\frac{4}{5}×3$
$=\frac{9×4×3}{10×5}$
$=\frac{108}{50}$
$=\frac{54}{25}$
$\frac{3}{10}×\frac{5}{6}×\frac{3}{5}$
$=\frac{3×5×3}{10×6×5}$
$=\frac{45}{300}$
$=\frac{3}{20}$
$\frac{1}{5}×\frac{10}{39}×\frac{13}{8}$
$=\frac{1×10×13}{5×39×8}$
$=\frac{130}{1560}$
$=\frac{1}{12}$
$\frac{4}{9}×36×\frac{5}{8}$
$=\frac{4×36×5}{9×8}$
$=\frac{720}{72}$
$=10$
$\frac{15}{16}×\frac{4}{25}×\frac{20}{3}$
$=\frac{15×4×20}{16×25×3}$
$=\frac{1200}{1200}$
$=1$
$\frac{10}{51}×\frac{6}{7}×\frac{34}{25}$
$=\frac{10×6×34}{51×7×25}$
$=\frac{2040}{8925}$
$=\frac{8}{35}$