一、口算。
$\frac{1}{2} × \frac{4}{17} =$
$\frac{2}{3} × \frac{8}{9} =$
$\frac{8}{9} - \frac{5}{12} =$
$\frac{1}{3} × \frac{9}{5} =$
$\frac{7}{12} × 0.75 =$
$1.2 × \frac{7}{9} =$
$80 × \frac{1}{16} =$
$\frac{5}{6} + \frac{1}{3} =$
$\frac{5}{8} × \frac{64}{75} =$
$\frac{7}{15} × \frac{1}{14} =$
$\frac{14}{15} × \frac{5}{6} =$
$\frac{3}{14} × \frac{5}{9} =$
$\frac{5}{8} × 24 =$
$0.15 × \frac{2}{5} =$
$\frac{1}{9} × \frac{3}{5} =$
$\frac{3}{2} × \frac{2}{21} =$
$\frac{4}{7} × \frac{3}{10} =$
$\frac{5}{12} × 1.5 =$
$\frac{18}{7} × \frac{2}{9} =$
$0.6 × \frac{4}{15} =$
$\frac{5}{4} × \frac{16}{15} =$

1.$\frac{2}{17}$ 2.$\frac{16}{27}$ 3.$\frac{17}{36}$ 4.$\frac{3}{5}$ 5.$\frac{7}{16}$ 6.$\frac{14}{15}$ 7.$5$ 8.$\frac{7}{6}$ 9.$\frac{8}{15}$ 10.$\frac{1}{30}$ 11.$\frac{7}{9}$ 12.$\frac{5}{42}$ 13.$15$ 14.$0.06$ 15.$\frac{1}{15}$ 16.$\frac{1}{7}$ 17.$\frac{6}{35}$ 18.$\frac{5}{8}$ 19.$\frac{4}{7}$ 20.$\frac{4}{25}$ 21.$\frac{4}{3}$

二、计算下面各题，能用简便算法的就用简便算法。
$\frac{5}{7} × \frac{5}{7} × \frac{9}{25}$
$42 × ( \frac{1}{6} - \frac{1}{7} )$
$16.5 × \frac{2}{5} - 1.5 × \frac{2}{5}$
$1000 × ( 1 + \frac{3}{8} )$
$\frac{2}{7} × \frac{3}{11} + \frac{3}{7} × \frac{9}{11}$
$\frac{4}{5} × \frac{2}{3} - \frac{1}{6} × 2$

1.$\frac{9}{49}$ 2.$1$ 3.$6$ 4.$1375$ 5.$\frac{3}{7}$ 6.$\frac{1}{5}$