一、口算。
$\frac{25}{9} × \frac{3}{5} =$
$\frac{5}{4} × \frac{12}{5} =$
$\frac{21}{4} × \frac{4}{7} =$
$\frac{2}{9} × \frac{3}{6} =$
$\frac{2}{3} × \frac{7}{8} =$
$\frac{4}{5} × \frac{7}{8} =$
$\frac{3}{16} × \frac{4}{15} =$
$\frac{3}{4} × \frac{2}{5} =$
$\frac{2}{3} × \frac{9}{8} =$
$\frac{5}{12} × \frac{3}{20} =$
$\frac{8}{15} × \frac{3}{2} =$
$\frac{9}{14} × \frac{7}{12} =$
$\frac{3}{4} × \frac{16}{9} =$
$\frac{7}{10} × \frac{3}{14} =$
$\frac{3}{8} × \frac{2}{9} =$
$\frac{6}{7} × \frac{3}{4} =$
$\frac{5}{8} × \frac{2}{5} =$
$\frac{4}{5} × \frac{5}{6} =$
$\frac{2}{3} × \frac{7}{12} =$
$\frac{4}{15} × \frac{5}{6} =$
$\frac{14}{3} × \frac{2}{7} =$

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

二、计算下面各题。
$\frac{90}{17}×\frac{34}{27}$
$\frac{80}{81}×\frac{45}{16}$
$\frac{36}{91}×\frac{13}{12}$
$\frac{3}{4}+0.4-\frac{7}{20}$
$\frac{7}{8}-0.75+\frac{9}{16}$
$0.8-\frac{2}{3}+\frac{1}{6}$

1.$\frac{20}{3}$ 2.$\frac{25}{9}$ 3.$\frac{3}{7}$ 4.$\frac{4}{5}$ 5.$\frac{11}{16}$ 6.$\frac{3}{10}$