一、口算。
$\frac {4}{5}-\frac {7}{10}=$ $40\% ×20\% =$ $4.72+1.5=$
$12.5÷50\% =$ $\frac {1}{2}×\frac {1}{3}=$ $\frac {4}{3}÷\frac {8}{9}=$
$80\% ÷\frac {5}{4}=$ $390×2\% =$ $0.9-0.26=$
$\frac {5}{12}÷\frac {5}{6}=$ $\frac {5}{9}×18=$ $\frac {9}{10}×\frac {15}{16}=$
$4.8÷12=$ $2.5+50\% =$ $80\% ×\frac {2}{5}=$
$23.4÷10=$ $\frac {7}{9}-30\% =$ $\frac {3}{4}÷\frac {4}{3}=$
$\frac {5}{8}×32\% =$ $\frac {5}{8}+\frac {1}{2}=$ $0.25×40\% =$

一、$\frac{1}{10}$ 0.08 6.22
25 $\frac{1}{6}$ $\frac{3}{2}$
$\frac{16}{25}$ 7.8 0.64
$\frac{1}{2}$ 10 $\frac{27}{32}$
0.4 3 0.32
2.34 $\frac{43}{90}$ $\frac{9}{16}$
$\frac{1}{5}$ $\frac{9}{8}$ 0.1

二、计算下面各题,怎样简便就怎样计算。
$\frac {2}{19}×32\% +\frac {17}{25}÷\frac {19}{2}$ $(84\% ×\frac {1}{3}+8.72)÷\frac {9}{10}$ $10\% ×\frac {2}{3}÷(80\% -\frac {1}{3})$
$16×\frac {7}{9}×6.25\% ×\frac {3}{7}$ $(\frac {1}{5}-\frac {1}{7})×50\% ×7$ $\frac {8}{15}÷[40\% ×(\frac {5}{2}+\frac {5}{6})]$

1. 计算$\frac{2}{19}×32\%+\frac{17}{25}÷\frac{19}{2}$
解：
将除法转化为乘法$\frac{17}{25}÷\frac{19}{2}=\frac{17}{25}×\frac{2}{19}$，$32\% = 0.32=\frac{8}{25}$
$\begin{aligned}&\frac{2}{19}×32\%+\frac{17}{25}÷\frac{19}{2}\\=&\frac{2}{19}×\frac{8}{25}+\frac{17}{25}×\frac{2}{19}\\=&\frac{2}{19}×(\frac{8}{25}+\frac{17}{25})\\=&\frac{2}{19}×1\\=&\frac{2}{19}\end{aligned}$
2. 计算$(84\%×\frac{1}{3}+8.72)÷\frac{9}{10}$
解：
$84\% = 0.84$
$\begin{aligned}&(84\%×\frac{1}{3}+8.72)÷\frac{9}{10}\\=&(0.84×\frac{1}{3}+8.72)×\frac{10}{9}\\=&(0.28 + 8.72)×\frac{10}{9}\\=&9×\frac{10}{9}\\=&10\end{aligned}$
3. 计算$10\%×\frac{2}{3}÷(80\%-\frac{1}{3})$
解：
$10\%=\frac{1}{10}$，$80\%=\frac{4}{5}$
$\begin{aligned}&10\%×\frac{2}{3}÷(80\%-\frac{1}{3})\\=&\frac{1}{10}×\frac{2}{3}÷(\frac{4}{5}-\frac{1}{3})\\=&\frac{1}{15}÷(\frac{12 - 5}{15})\\=&\frac{1}{15}÷\frac{7}{15}\\=&\frac{1}{7}\end{aligned}$
4. 计算$16×\frac{7}{9}×6.25\%×\frac{3}{7}$
解：
$6.25\%=\frac{1}{16}$
$\begin{aligned}&16×\frac{7}{9}×6.25\%×\frac{3}{7}\\=&16×\frac{1}{16}×(\frac{7}{9}×\frac{3}{7})\\=&1×\frac{1}{3}\\=&\frac{1}{3}\end{aligned}$
5. 计算$(\frac{1}{5}-\frac{1}{7})×50\%×7$
解：
$\begin{aligned}&(\frac{1}{5}-\frac{1}{7})×50\%×7\\=&(\frac{1}{5}-\frac{1}{7})×7×\frac{1}{2}\\=&(\frac{7}{5}- 1)×\frac{1}{2}\\=&\frac{2}{5}×\frac{1}{2}\\=&\frac{1}{5}\end{aligned}$
6. 计算$\frac{8}{15}÷[40\%×(\frac{5}{2}+\frac{5}{6})]$
解：
$40\%=\frac{2}{5}$
$\begin{aligned}&\frac{8}{15}÷[40\%×(\frac{5}{2}+\frac{5}{6})]\\=&\frac{8}{15}÷[\frac{2}{5}×(\frac{15 + 5}{6})]\\=&\frac{8}{15}÷(\frac{2}{5}×\frac{20}{6})\\=&\frac{8}{15}÷\frac{4}{3}\\=&\frac{8}{15}×\frac{3}{4}\\=&\frac{2}{5}\end{aligned}$
综上，答案依次为$\frac{2}{19}$；$10$；$\frac{1}{7}$；$\frac{1}{3}$；$\frac{1}{5}$；$\frac{2}{5}$。