一、口算。
$\frac{3}{7} ÷ \frac{1}{7} =$
$1.6 × \frac{2}{3} =$
$\frac{1}{2} + \frac{2}{7} =$
$\frac{9}{10} × \frac{5}{6} =$
$\frac{5}{8} + \frac{1}{4} =$
$\frac{3}{4} ÷ 12 =$
$6 × \frac{5}{8} =$
$\frac{3}{2} ÷ \frac{5}{2} =$
$\frac{3}{7} ÷ \frac{7}{12} =$
$\frac{4}{5} ÷ \frac{4}{3} =$
$\frac{7}{2} × \frac{4}{21} =$
$\frac{7}{6} - \frac{3}{4} =$
$\frac{10}{9} ÷ 5 =$
$\frac{5}{6} ÷ \frac{5}{12} =$
$\frac{3}{4} × \frac{2}{3} =$
$14 × \frac{2}{21} =$
$\frac{1}{5} ÷ \frac{3}{10} =$
$\frac{9}{10} - \frac{2}{5} =$
$\frac{3}{5} ÷ \frac{9}{10} =$
$\frac{7}{2} ÷ \frac{14}{15} =$
$\frac{2}{3} × \frac{3}{11} =$

1.$3$ 2.$\frac{16}{15}$ 3.$\frac{11}{14}$ 4.$\frac{3}{4}$ 5.$\frac{7}{8}$ 6.$\frac{1}{16}$ 7.$\frac{15}{4}$ 8.$\frac{3}{5}$ 9.$\frac{36}{49}$ 10.$\frac{3}{5}$ 11.$\frac{2}{3}$ 12.$\frac{5}{12}$ 13.$\frac{2}{9}$ 14.$2$ 15.$\frac{1}{2}$ 16.$\frac{4}{3}$ 17.$\frac{2}{3}$ 18.$\frac{1}{2}$ 19.$\frac{2}{3}$ 20.$\frac{15}{4}$ 21.$\frac{2}{11}$

二、计算下面各题，能用简便算法的就用简便算法。
$\frac{36}{49} ÷ \frac{3}{7} ÷ \frac{4}{3}$
$( \frac{4}{13} + \frac{1}{23} ) × 13 + \frac{10}{23}$
$\frac{25}{9} × \frac{3}{4} - \frac{7}{9} ÷ \frac{4}{3}$
$\frac{14}{13} × \frac{10}{9} - \frac{10}{13} × \frac{1}{9}$
$[ \frac{5}{3} - ( \frac{2}{5} + \frac{1}{4} ) ] ÷ \frac{61}{4}$
$\frac{11}{12} ÷ ( 1 - \frac{1}{6} - \frac{3}{8} )$

1.$\frac{9}{7}$ 2.$5$ 3.$\frac{3}{2}$ 4.$\frac{10}{9}$ 5.$\frac{1}{15}$ 6.$2$