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（1）直接写得数。
$21× \frac{4}{7}=$ $\frac{6}{11}× \frac{11}{9}=$ $\frac{7}{5}÷ \frac{5}{9}=$ $\frac{3}{4}÷5=$
$\frac{7}{8}×4.8=$ $\frac{7}{12}÷ \frac{7}{24}=$ $\frac{3}{10}÷ \frac{2}{5}=$ $\frac{2}{3}× \frac{5}{6}=$
$0÷ \frac{4}{5}=$ $45× \frac{8}{9}=$ $\frac{1}{88}× \frac{88}{99}=$ $\frac{3}{25}÷ \frac{3}{25}=$
（2）计算下列各题,能简算的要简算。
$(\frac{1}{5}-\frac{1}{8})×40$ $1-\frac{5}{24}-\frac{19}{24}$ $\frac{1}{3}÷5+\frac{1}{4}÷5$
$(\frac{5}{24}+\frac{11}{12}-\frac{2}{3})×48$ $(\frac{3}{7}+\frac{1}{9})×7+\frac{2}{9}$ $\frac{16}{11}-(\frac{5}{11}-\frac{3}{13})$
$\frac{8}{15}×(15-\frac{15}{8})$ $\frac{16}{25}÷ \frac{8}{5}+\frac{9}{25}× \frac{5}{8}$ $\frac{7}{25}÷[(\frac{4}{5}-\frac{1}{10})× \frac{4}{7}]$
$21× \frac{4}{7}=$ $\frac{6}{11}× \frac{11}{9}=$ $\frac{7}{5}÷ \frac{5}{9}=$ $\frac{3}{4}÷5=$
$\frac{7}{8}×4.8=$ $\frac{7}{12}÷ \frac{7}{24}=$ $\frac{3}{10}÷ \frac{2}{5}=$ $\frac{2}{3}× \frac{5}{6}=$
$0÷ \frac{4}{5}=$ $45× \frac{8}{9}=$ $\frac{1}{88}× \frac{88}{99}=$ $\frac{3}{25}÷ \frac{3}{25}=$
（2）计算下列各题,能简算的要简算。
$(\frac{1}{5}-\frac{1}{8})×40$ $1-\frac{5}{24}-\frac{19}{24}$ $\frac{1}{3}÷5+\frac{1}{4}÷5$
$(\frac{5}{24}+\frac{11}{12}-\frac{2}{3})×48$ $(\frac{3}{7}+\frac{1}{9})×7+\frac{2}{9}$ $\frac{16}{11}-(\frac{5}{11}-\frac{3}{13})$
$\frac{8}{15}×(15-\frac{15}{8})$ $\frac{16}{25}÷ \frac{8}{5}+\frac{9}{25}× \frac{5}{8}$ $\frac{7}{25}÷[(\frac{4}{5}-\frac{1}{10})× \frac{4}{7}]$
答案
（1）直接写得数
$21× \frac{4}{7}=12$
$\frac{6}{11}× \frac{11}{9}=\frac{2}{3}$
$\frac{7}{5}÷ \frac{5}{9}=\frac{63}{25}$
$\frac{3}{4}÷5=\frac{3}{20}$
$\frac{7}{8}×4.8=4.2$
$\frac{7}{12}÷ \frac{7}{24}=2$
$\frac{3}{10}÷ \frac{2}{5}=\frac{3}{4}$
$\frac{2}{3}× \frac{5}{6}=\frac{5}{9}$
$0÷ \frac{4}{5}=0$
$45× \frac{8}{9}=40$
$\frac{1}{88}× \frac{88}{99}=\frac{1}{99}$
$\frac{3}{25}÷ \frac{3}{25}=1$
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（2）计算下列各题，能简算的要简算
$\begin{aligned}&(\frac{1}{5}-\frac{1}{8})×40\\=&\frac{1}{5}×40-\frac{1}{8}×40\\=&8-5\\=&3\end{aligned}$
$\begin{aligned}&1-\frac{5}{24}-\frac{19}{24}\\=&1-(\frac{5}{24}+\frac{19}{24})\\=&1-1\\=&0\end{aligned}$
$\begin{aligned}&\frac{1}{3}÷5+\frac{1}{4}÷5\\=&\frac{1}{3}×\frac{1}{5}+\frac{1}{4}×\frac{1}{5}\\=&(\frac{1}{3}+\frac{1}{4})×\frac{1}{5}\\=&\frac{7}{12}×\frac{1}{5}\\=&\frac{7}{60}\end{aligned}$
$\begin{aligned}&(\frac{5}{24}+\frac{11}{12}-\frac{2}{3})×48\\=&\frac{5}{24}×48+\frac{11}{12}×48-\frac{2}{3}×48\\=&10+44-32\\=&22\end{aligned}$
$\begin{aligned}&(\frac{3}{7}+\frac{1}{9})×7+\frac{2}{9}\\=&\frac{3}{7}×7+\frac{1}{9}×7+\frac{2}{9}\\=&3+\frac{7}{9}+\frac{2}{9}\\=&3+(\frac{7}{9}+\frac{2}{9})\\=&3+1\\=&4\end{aligned}$
$\begin{aligned}&\frac{16}{11}-(\frac{5}{11}-\frac{3}{13})\\=&\frac{16}{11}-\frac{5}{11}+\frac{3}{13}\\=&1+\frac{3}{13}\\=&\frac{16}{13}\end{aligned}$
$\begin{aligned}&\frac{8}{15}×(15-\frac{15}{8})\\=&\frac{8}{15}×15-\frac{8}{15}×\frac{15}{8}\\=&8-1\\=&7\end{aligned}$
$\begin{aligned}&\frac{16}{25}÷ \frac{8}{5}+\frac{9}{25}× \frac{5}{8}\\=&\frac{16}{25}×\frac{5}{8}+\frac{9}{25}×\frac{5}{8}\\=&(\frac{16}{25}+\frac{9}{25})×\frac{5}{8}\\=&1×\frac{5}{8}\\=&\frac{5}{8}\end{aligned}$
$\begin{aligned}&\frac{7}{25}÷[(\frac{4}{5}-\frac{1}{10})× \frac{4}{7}]\\=&\frac{7}{25}÷[\frac{7}{10}×\frac{4}{7}]\\=&\frac{7}{25}÷\frac{2}{5}\\=&\frac{7}{10}\end{aligned}$
$21× \frac{4}{7}=12$
$\frac{6}{11}× \frac{11}{9}=\frac{2}{3}$
$\frac{7}{5}÷ \frac{5}{9}=\frac{63}{25}$
$\frac{3}{4}÷5=\frac{3}{20}$
$\frac{7}{8}×4.8=4.2$
$\frac{7}{12}÷ \frac{7}{24}=2$
$\frac{3}{10}÷ \frac{2}{5}=\frac{3}{4}$
$\frac{2}{3}× \frac{5}{6}=\frac{5}{9}$
$0÷ \frac{4}{5}=0$
$45× \frac{8}{9}=40$
$\frac{1}{88}× \frac{88}{99}=\frac{1}{99}$
$\frac{3}{25}÷ \frac{3}{25}=1$
---
（2）计算下列各题，能简算的要简算
$\begin{aligned}&(\frac{1}{5}-\frac{1}{8})×40\\=&\frac{1}{5}×40-\frac{1}{8}×40\\=&8-5\\=&3\end{aligned}$
$\begin{aligned}&1-\frac{5}{24}-\frac{19}{24}\\=&1-(\frac{5}{24}+\frac{19}{24})\\=&1-1\\=&0\end{aligned}$
$\begin{aligned}&\frac{1}{3}÷5+\frac{1}{4}÷5\\=&\frac{1}{3}×\frac{1}{5}+\frac{1}{4}×\frac{1}{5}\\=&(\frac{1}{3}+\frac{1}{4})×\frac{1}{5}\\=&\frac{7}{12}×\frac{1}{5}\\=&\frac{7}{60}\end{aligned}$
$\begin{aligned}&(\frac{5}{24}+\frac{11}{12}-\frac{2}{3})×48\\=&\frac{5}{24}×48+\frac{11}{12}×48-\frac{2}{3}×48\\=&10+44-32\\=&22\end{aligned}$
$\begin{aligned}&(\frac{3}{7}+\frac{1}{9})×7+\frac{2}{9}\\=&\frac{3}{7}×7+\frac{1}{9}×7+\frac{2}{9}\\=&3+\frac{7}{9}+\frac{2}{9}\\=&3+(\frac{7}{9}+\frac{2}{9})\\=&3+1\\=&4\end{aligned}$
$\begin{aligned}&\frac{16}{11}-(\frac{5}{11}-\frac{3}{13})\\=&\frac{16}{11}-\frac{5}{11}+\frac{3}{13}\\=&1+\frac{3}{13}\\=&\frac{16}{13}\end{aligned}$
$\begin{aligned}&\frac{8}{15}×(15-\frac{15}{8})\\=&\frac{8}{15}×15-\frac{8}{15}×\frac{15}{8}\\=&8-1\\=&7\end{aligned}$
$\begin{aligned}&\frac{16}{25}÷ \frac{8}{5}+\frac{9}{25}× \frac{5}{8}\\=&\frac{16}{25}×\frac{5}{8}+\frac{9}{25}×\frac{5}{8}\\=&(\frac{16}{25}+\frac{9}{25})×\frac{5}{8}\\=&1×\frac{5}{8}\\=&\frac{5}{8}\end{aligned}$
$\begin{aligned}&\frac{7}{25}÷[(\frac{4}{5}-\frac{1}{10})× \frac{4}{7}]\\=&\frac{7}{25}÷[\frac{7}{10}×\frac{4}{7}]\\=&\frac{7}{25}÷\frac{2}{5}\\=&\frac{7}{10}\end{aligned}$
