一、口算。
$\frac{4}{5} × \frac{5}{16} =$
$\frac{7}{12} × \frac{4}{7} =$
$\frac{5}{7} × \frac{2}{5} =$
$\frac{4}{9} × \frac{3}{16} =$
$\frac{3}{4} × \frac{1}{5} =$
$\frac{4}{9} × \frac{3}{2} =$
$\frac{3}{10} × \frac{1}{6} =$
$\frac{18}{25} × \frac{5}{16} =$
$\frac{17}{19} × \frac{38}{51} =$
$\frac{3}{4} × \frac{20}{9} =$
$\frac{2}{3} × \frac{11}{12} =$
$\frac{1}{2} × \frac{3}{8} =$
$\frac{7}{9} × \frac{9}{28} =$
$\frac{5}{6} × \frac{8}{15} =$
$\frac{3}{5} × \frac{5}{9} =$
$\frac{9}{14} × \frac{7}{18} =$
$\frac{4}{5} × \frac{4}{7} =$
$\frac{11}{15} × \frac{25}{33} =$
$\frac{3}{4} × \frac{6}{5} =$
$\frac{3}{11} × \frac{22}{9} =$
$\frac{5}{12} × \frac{2}{3} =$

1.$\frac{1}{4}$ 2.$\frac{1}{3}$ 3.$\frac{2}{7}$ 4.$\frac{1}{12}$ 5.$\frac{3}{20}$ 6.$\frac{2}{3}$ 7.$\frac{1}{20}$ 8.$\frac{9}{40}$ 9.$\frac{2}{3}$ 10.$\frac{5}{3}$ 11.$\frac{11}{18}$ 12.$\frac{3}{16}$ 13.$\frac{1}{4}$ 14.$\frac{4}{9}$ 15.$\frac{1}{3}$ 16.$\frac{1}{4}$ 17.$\frac{16}{35}$ 18.$\frac{5}{9}$ 19.$\frac{9}{10}$ 20.$\frac{2}{3}$ 21.$\frac{5}{18}$

二、计算下面各题。
$\frac{7}{120} × \frac{24}{49}$
$\frac{64}{95} × \frac{19}{32}$
$\frac{128}{105} × \frac{7}{16}$
$\frac{9}{10} - \frac{2}{5} + \frac{3}{4}$
$\frac{8}{9} - (\frac{2}{3} + \frac{1}{6})$
$6.23 - \frac{2}{7} + 2.77 - \frac{5}{7}$

1.$\frac{1}{35}$ 2.$\frac{2}{5}$ 3.$\frac{8}{15}$ 4.$\frac{5}{4}$ 5.$\frac{1}{18}$ 6.$8$