1. 填一填。
(1) $\frac{b}{a}×\frac{d}{c}=\frac{(\quad)}{(\quad)}(a,c≠0)$ $\frac{b}{a}÷\frac{d}{c}=\frac{(\quad)}{(\quad)}×\frac{(\quad)}{(\quad)}(a,c,d≠0)$
(2) 看图列式计算。

(1) $\frac{b}{a}×\frac{d}{c}=\frac{bd}{ac}$
$\frac{b}{a}÷\frac{d}{c}=\frac{b}{a}×\frac{c}{d}$
(2) $\frac{2}{3}×\frac{1}{2}=\frac{1}{3}$
$\frac{1}{3}×\frac{1}{4}=\frac{1}{12}$

2. 直接写出得数。
$\frac{3}{5}×\frac{1}{2}=$
$\frac{3}{4}×\frac{2}{3}=$
$\frac{4}{7}÷4=$
$\frac{5}{6}÷\frac{5}{2}=$
$4.5×\frac{2}{9}=$
$\frac{7}{10}×\frac{5}{14}=$
$\frac{5}{8}÷\frac{5}{6}=$
$\frac{5}{7}×0.2=$

$\frac{3}{5}×\frac{1}{2}=\frac{3}{10}$
$\frac{3}{4}×\frac{2}{3}=\frac{1}{2}$
$\frac{4}{7}÷4=\frac{1}{7}$
$\frac{5}{6}÷\frac{5}{2}=\frac{1}{3}$
$4.5×\frac{2}{9}=1$
$\frac{7}{10}×\frac{5}{14}=\frac{1}{4}$
$\frac{5}{8}÷\frac{5}{6}=\frac{3}{4}$
$\frac{5}{7}×0.2=\frac{1}{7}$

3. 计算下列各题。
(1) $\frac{7}{10}×\frac{5}{6}-\frac{1}{4}$
$\frac{3}{8}÷12+\frac{3}{4}×\frac{1}{12}$
$\frac{5}{6}÷\frac{4}{9}÷\frac{5}{18}$
$\frac{3}{4}×18+\frac{1}{4}×6$
(2) $48×\frac{4}{5}+1÷\frac{5}{8}$
$\frac{2}{7}×(\frac{4}{9}-\frac{1}{6})÷\frac{4}{21}$

$\frac{7}{10}×\frac{5}{6}-\frac{1}{4}$
$=\frac{7}{12}-\frac{1}{4}$
$=\frac{7}{12}-\frac{3}{12}$
$=\frac{1}{3}$
$\frac{3}{8}÷12+\frac{3}{4}×\frac{1}{12}$
$=\frac{3}{8}×\frac{1}{12}+\frac{3}{4}×\frac{1}{12}$
$=(\frac{3}{8}+\frac{3}{4})×\frac{1}{12}$
$=\frac{9}{8}×\frac{1}{12}$
$=\frac{3}{32}$
$\frac{5}{6}÷\frac{4}{9}÷\frac{5}{18}$
$=\frac{5}{6}×\frac{9}{4}×\frac{18}{5}$
$=\frac{27}{4}$
$\frac{3}{4}×18+\frac{1}{4}×6$
$=\frac{54}{4}+\frac{6}{4}$
$=15$
$48×\frac{4}{5}+1÷\frac{5}{8}$
$=\frac{192}{5}+\frac{8}{5}$
$=40$
$\frac{2}{7}×(\frac{4}{9}-\frac{1}{6})÷\frac{4}{21}$
$=\frac{2}{7}×\frac{5}{18}×\frac{21}{4}$
$=\frac{5}{12}$