1. 计算下面各题。
$24÷\frac{3}{8}= $
$\frac{81}{82}÷18= $
$\frac{15}{19}÷\frac{5}{57}= $
$\frac{31}{32}÷\frac{31}{64}= $
$\frac{7}{15}÷\frac{14}{5}×\frac{3}{2}= $
$\frac{9}{34}÷\frac{6}{17}÷\frac{9}{8}= $
$\frac{5}{6}÷(\frac{1}{12}+\frac{1}{8})= $
$\frac{9}{10}÷\frac{5}{8}÷\frac{7}{5}= $

1. 64；$\frac{9}{164}$；9；2；$\frac{1}{4}$；$\frac{2}{3}$；4；$\frac{36}{35}$

$24÷\frac{3}{8}=24×\frac{8}{3}=64$
$\frac{81}{82}÷18=\frac{81}{82}×\frac{1}{18}=\frac{9}{164}$
$\frac{15}{19}÷\frac{5}{57}=\frac{15}{19}×\frac{57}{5}=9$
$\frac{31}{32}÷\frac{31}{64}=\frac{31}{32}×\frac{64}{31}=2$
$\frac{7}{15}÷\frac{14}{5}×\frac{3}{2}=\frac{7}{15}×\frac{5}{14}×\frac{3}{2}=\frac{1}{6}×\frac{3}{2}=\frac{1}{4}$
$\frac{9}{34}÷\frac{6}{17}÷\frac{9}{8}=\frac{9}{34}×\frac{17}{6}×\frac{8}{9}=\frac{3}{4}×\frac{8}{9}=\frac{2}{3}$
$\frac{5}{6}÷(\frac{1}{12}+\frac{1}{8})=\frac{5}{6}÷(\frac{2}{24}+\frac{3}{24})=\frac{5}{6}÷\frac{5}{24}=\frac{5}{6}×\frac{24}{5}=4$
$\frac{9}{10}÷\frac{5}{8}÷\frac{7}{5}=\frac{9}{10}×\frac{8}{5}×\frac{5}{7}=\frac{36}{25}×\frac{5}{7}=\frac{36}{35}$

2. 解下列方程。
$\frac{2}{3}x= \frac{5}{6}$
$\frac{7}{9}x-\frac{2}{3}x= 16$
$\frac{2}{7}x= \frac{1}{2}×\frac{3}{14}$
$6-\frac{3}{8}x= 0.75$
$(2-\frac{3}{4})x= \frac{4}{5}$
$\frac{8}{15}x÷\frac{14}{3}= \frac{2}{7}$
$x÷\frac{1}{2}= \frac{4}{9}×0.25$
$(\frac{2}{3}-\frac{1}{4})x÷\frac{5}{7}= \frac{28}{5}$

2. $x=\frac{5}{4}$；$x=144$；$x=\frac{3}{8}$；$x=14$；$x=\frac{16}{25}$；$x=\frac{5}{2}$；$x=\frac{1}{18}$；$x=\frac{48}{5}$

$\frac{2}{3}x=\frac{5}{6}$
解：$x=\frac{5}{6}÷\frac{2}{3}$
$x=\frac{5}{6}×\frac{3}{2}$
$x=\frac{5}{4}$
$\frac{7}{9}x-\frac{2}{3}x=16$
解：$\frac{7}{9}x-\frac{6}{9}x=16$
$\frac{1}{9}x=16$
$x=16×9$
$x=144$
$\frac{2}{7}x=\frac{1}{2}×\frac{3}{14}$
解：$\frac{2}{7}x=\frac{3}{28}$
$x=\frac{3}{28}÷\frac{2}{7}$
$x=\frac{3}{28}×\frac{7}{2}$
$x=\frac{3}{8}$
$6-\frac{3}{8}x=0.75$
解：$\frac{3}{8}x=6 - 0.75$
$\frac{3}{8}x=5.25$
$x=5.25÷\frac{3}{8}$
$x=5.25×\frac{8}{3}$
$x=14$
$(2-\frac{3}{4})x=\frac{4}{5}$
解：$\frac{5}{4}x=\frac{4}{5}$
$x=\frac{4}{5}÷\frac{5}{4}$
$x=\frac{4}{5}×\frac{4}{5}$
$x=\frac{16}{25}$
$\frac{8}{15}x÷\frac{14}{3}=\frac{2}{7}$
解：$\frac{8}{15}x=\frac{2}{7}×\frac{14}{3}$
$\frac{8}{15}x=\frac{4}{3}$
$x=\frac{4}{3}÷\frac{8}{15}$
$x=\frac{4}{3}×\frac{15}{8}$
$x=\frac{5}{2}$
$x÷\frac{1}{2}=\frac{4}{9}×0.25$
解：$x÷\frac{1}{2}=\frac{4}{9}×\frac{1}{4}$
$x÷\frac{1}{2}=\frac{1}{9}$
$x=\frac{1}{9}×\frac{1}{2}$
$x=\frac{1}{18}$
$(\frac{2}{3}-\frac{1}{4})x÷\frac{5}{7}=\frac{28}{5}$
解：$(\frac{8}{12}-\frac{3}{12})x÷\frac{5}{7}=\frac{28}{5}$
$\frac{5}{12}x÷\frac{5}{7}=\frac{28}{5}$
$\frac{5}{12}x=\frac{28}{5}×\frac{5}{7}$
$\frac{5}{12}x=4$
$x=4÷\frac{5}{12}$
$x=4×\frac{12}{5}$
$x=\frac{48}{5}$

3. 根据题意,选择合适的条件和算式用线连起来。
五年级有学生 120 人,______,六年级有学生多少人？
|六年级学生是五年级的$\frac{4}{5}$| $120÷(1-\frac{1}{5})$|
|五年级学生是六年级的$\frac{4}{5}$| $120×(1+\frac{1}{5})$|
|五年级学生比六年级少$\frac{1}{5}$| $120÷\frac{4}{5}$|
|六年级学生比五年级多$\frac{1}{5}$| $120×\frac{4}{5}$|
|五年级学生比六年级多$\frac{1}{5}$| $120÷(1+\frac{1}{5})$|
|六年级学生比五年级少$\frac{1}{5}$| $120×(1-\frac{1}{5})$|

3.