一、口算。
$\frac {2}{15}+\frac {1}{5}=$
$\frac {3}{8}×\frac {2}{15}=$
$\frac {3}{2}-\frac {2}{3}=$
$\frac {15}{16}×\frac {2}{3}=$
$\frac {44}{75}×\frac {5}{11}=$
$\frac {5}{6}×48=$
$49×\frac {4}{7}=$
$\frac {5}{24}×120=$
$\frac {3}{8}×\frac {8}{9}=$
$\frac {4}{15}+\frac {5}{12}=$
$\frac {7}{9}×\frac {9}{35}=$
$\frac {3}{4}×3=$
$7×\frac {4}{15}=$
$\frac {2}{3}×\frac {4}{5}=$
$\frac {7}{12}×\frac {5}{6}=$
$\frac {8}{9}×27=$
$\frac {6}{11}×\frac {3}{4}=$
$14×\frac {1}{8}=$
$0.375×\frac {4}{9}=$
$\frac {3}{4}-\frac {1}{2}=$
$\frac {1}{3}×\frac {30}{31}=$

$\frac{1}{3}$ $\frac{1}{20}$ $\frac{5}{6}$ $\frac{5}{8}$ $\frac{4}{15}$ 40 28 25 $\frac{1}{3}$ $\frac{41}{60}$ $\frac{1}{5}$ $\frac{9}{4}$ $\frac{28}{15}$ $\frac{8}{15}$ $\frac{35}{72}$ 24 $\frac{9}{22}$ $\frac{7}{4}$ $\frac{1}{6}$ $\frac{1}{4}$ $\frac{10}{31}$

$\frac{2}{15}+\frac{1}{5}=\frac{2}{15}+\frac{3}{15}=\frac{5}{15}=\frac{1}{3}$
$\frac{3}{8}×\frac{2}{15}=\frac{3×2}{8×15}=\frac{6}{120}=\frac{1}{20}$
$\frac{3}{2}-\frac{2}{3}=\frac{9}{6}-\frac{4}{6}=\frac{5}{6}$
$\frac{15}{16}×\frac{2}{3}=\frac{15×2}{16×3}=\frac{30}{48}=\frac{5}{8}$
$\frac{44}{75}×\frac{5}{11}=\frac{44×5}{75×11}=\frac{220}{825}=\frac{4}{15}$
$\frac{5}{6}×48=5×8=40$
$49×\frac{4}{7}=7×4=28$
$\frac{5}{24}×120=5×5=25$
$\frac{3}{8}×\frac{8}{9}=\frac{3×8}{8×9}=\frac{24}{72}=\frac{1}{3}$
$\frac{4}{15}+\frac{5}{12}=\frac{16}{60}+\frac{25}{60}=\frac{41}{60}$
$\frac{7}{9}×\frac{9}{35}=\frac{7×9}{9×35}=\frac{63}{315}=\frac{1}{5}$
$\frac{3}{4}×3=\frac{9}{4}$
$7×\frac{4}{15}=\frac{28}{15}$
$\frac{2}{3}×\frac{4}{5}=\frac{8}{15}$
$\frac{7}{12}×\frac{5}{6}=\frac{35}{72}$
$\frac{8}{9}×27=8×3=24$
$\frac{6}{11}×\frac{3}{4}=\frac{18}{44}=\frac{9}{22}$
$14×\frac{1}{8}=\frac{14}{8}=\frac{7}{4}$
$0.375×\frac{4}{9}=\frac{3}{8}×\frac{4}{9}=\frac{12}{72}=\frac{1}{6}$
$\frac{3}{4}-\frac{1}{2}=\frac{3}{4}-\frac{2}{4}=\frac{1}{4}$
$\frac{1}{3}×\frac{30}{31}=\frac{30}{93}=\frac{10}{31}$

二、计算下面各题。
$\frac {3}{16}×\frac {3}{4}×\frac {8}{27}$
$\frac {7}{8}×20×8$
$\frac {3}{4}×6×\frac {5}{18}$
$36×\frac {1}{54}×\frac {9}{4}$
$\frac {19}{13}×\frac {26}{57}×\frac {3}{4}$
$\frac {26}{63}×\frac {28}{39}×\frac {27}{64}$

$\frac{1}{24}$ 140 $\frac{5}{4}$ $\frac{3}{2}$ $\frac{1}{2}$ $\frac{1}{8}$

$\frac{3}{16}×\frac{3}{4}×\frac{8}{27}$
$=\frac{3×3×8}{16×4×27}$
$=\frac{72}{1728}$
$=\frac{1}{24}$
$\frac{7}{8}×20×8$
$=\frac{7}{8}×8×20$
$=7×20$
$=140$
$\frac{3}{4}×6×\frac{5}{18}$
$=\frac{3×6×5}{4×18}$
$=\frac{90}{72}$
$=\frac{5}{4}$
$36×\frac{1}{54}×\frac{9}{4}$
$=\frac{36×1×9}{54×4}$
$=\frac{324}{216}$
$=\frac{3}{2}$
$\frac{19}{13}×\frac{26}{57}×\frac{3}{4}$
$=\frac{19×26×3}{13×57×4}$
$=\frac{1482}{3036}$
$=\frac{1}{2}$
$\frac{26}{63}×\frac{28}{39}×\frac{27}{64}$
$=\frac{26×28×27}{63×39×64}$
$=\frac{19656}{156288}$
$=\frac{1}{8}$