1. 直接写出得数。
$\frac{5}{9} × 72 =$
$\frac{4}{5} × \frac{15}{16} =$
$25 × \frac{3}{20} =$
$3.6 ÷ \frac{9}{10} =$
$4.5 × \frac{7}{9} =$
$0.4 - 0.31 =$
$\frac{5}{6} + \frac{1}{2} =$
$\frac{3}{13} × \frac{26}{27} =$
$\frac{3}{4} ÷ \frac{5}{6} =$
$\frac{1}{7} + \frac{1}{8} =$
$75\% - 50\% =$
$\frac{7}{12} - \frac{1}{4} =$
$3.14 × 6 =$
$25\% + \frac{3}{4} =$
$\frac{7}{9} ÷ \frac{7}{11} =$
$10 + 10\% =$

$\frac{5}{9} × 72 = 40$
$\frac{4}{5} × \frac{15}{16} = \frac{3}{4}$
$25 × \frac{3}{20} = \frac{15}{4}$（或3.75）
$3.6 ÷ \frac{9}{10} = 4$
$4.5 × \frac{7}{9} = 3.5$
$0.4 - 0.31 = 0.09$
$\frac{5}{6} + \frac{1}{2} = \frac{4}{3}$
$\frac{3}{13} × \frac{26}{27} = \frac{2}{9}$
$\frac{3}{4} ÷ \frac{5}{6} = \frac{9}{10}$
$\frac{1}{7} + \frac{1}{8} = \frac{15}{56}$
$75\% - 50\% = 0.25$
$\frac{7}{12} - \frac{1}{4} = \frac{1}{3}$
$3.14 × 6 = 18.84$
$25\% + \frac{3}{4} = 1$
$\frac{7}{9} ÷ \frac{7}{11} = \frac{11}{9}$
$10 + 10\% = 10.1$

2. 计算下面各题。
$\frac{4}{9} × \frac{3}{8} ÷ \frac{2}{5}$
$\frac{7}{12} × \frac{5}{6} + \frac{7}{12} × \frac{1}{6}$
$\frac{5}{6} ÷ ( \frac{3}{4} × \frac{2}{9} )$

$\frac{4}{9}×\frac{3}{8}÷\frac{2}{5}$
$=\frac{4}{9}×\frac{3}{8}×\frac{5}{2}$
$=\frac{1}{6}×\frac{5}{2}$
$=\frac{5}{12}$
$\frac{7}{12}×\frac{5}{6}+\frac{7}{12}×\frac{1}{6}$
$=\frac{7}{12}×(\frac{5}{6}+\frac{1}{6})$
$=\frac{7}{12}×1$
$=\frac{7}{12}$
$\frac{5}{6}÷(\frac{3}{4}×\frac{2}{9})$
$=\frac{5}{6}÷\frac{1}{6}$
$=\frac{5}{6}×6$
$=5$

3.连一连。

某小学开展兴趣社团活动。参加体育社团的人数占社团总人数的$\frac{2}{5}$，参加艺术社团的人数是参加体育社团的$\frac{3}{4}$，体育社团和艺术社团共有210人。该校社团共有多少人？
反思 我错了（）道题。 自我评价：

连线题计算与对应
$4×\frac{3}{8}÷\frac{1}{2}=3$
$0.8×\frac{5}{2}×2=4$
$2×\frac{3}{4}+0.5=2$
$12×\frac{5}{18}÷\frac{5}{6}=4$
$\frac{8}{3}-\frac{4}{3}×\frac{1}{2}=2$
$1.5×\frac{4}{3}÷\frac{2}{3}=3$
连线结果：
$4×\frac{3}{8}÷\frac{1}{2}$ 连 $1.5×\frac{4}{3}÷\frac{2}{3}$
$0.8×\frac{5}{2}×2$ 连 $12×\frac{5}{18}÷\frac{5}{6}$
$2×\frac{3}{4}+0.5$ 连 $\frac{8}{3}-\frac{4}{3}×\frac{1}{2}$
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应用题
$\begin{aligned}210÷(\frac{2}{5} + \frac{2}{5}×\frac{3}{4})&=210÷\frac{7}{10}\\&=300\end{aligned}$
答：该校社团共有300人。