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(1)$\frac{5}{7}$除以它的倒数，商是（）。
答案
$\frac{5}{7}$的倒数是$\frac{7}{5}$
$\frac{5}{7} ÷ \frac{7}{5} = \frac{5}{7} × \frac{5}{7} = \frac{25}{49}$
商是($\frac{25}{49}$)。
$\frac{5}{7} ÷ \frac{7}{5} = \frac{5}{7} × \frac{5}{7} = \frac{25}{49}$
商是($\frac{25}{49}$)。
(2)20 t是()t的$\frac{2}{5}$,4 km的$\frac{3}{10}$与3 km的()长度相等。
答案
$20÷\frac{2}{5}=50(\mathrm{t})$
$4×\frac{3}{10}=\frac{6}{5}(\mathrm{km})$
$\frac{6}{5}÷3=\frac{2}{5}$
答：20 t是50 t的$\frac{2}{5}$，4 km的$\frac{3}{10}$与3 km的$\frac{2}{5}$长度相等。
$4×\frac{3}{10}=\frac{6}{5}(\mathrm{km})$
$\frac{6}{5}÷3=\frac{2}{5}$
答：20 t是50 t的$\frac{2}{5}$，4 km的$\frac{3}{10}$与3 km的$\frac{2}{5}$长度相等。
(3)在○里填上“＞”“＜”或“=”。
$\frac{2}{15} ÷ \frac{5}{7} ◯ \frac{2}{15}$
$\frac{1}{7} ÷ 4 ◯ \frac{1}{7}$
$\frac{9}{8} ◯ \frac{9}{8} ÷ 1$
$\frac{15}{34} ÷ \frac{15}{34} ◯ \frac{15}{34}$
$\frac{2}{15} ÷ \frac{5}{7} ◯ \frac{2}{15}$
$\frac{1}{7} ÷ 4 ◯ \frac{1}{7}$
$\frac{9}{8} ◯ \frac{9}{8} ÷ 1$
$\frac{15}{34} ÷ \frac{15}{34} ◯ \frac{15}{34}$
答案
$\frac{2}{15} ÷ \frac{5}{7} ＞ \frac{2}{15}$
$\frac{1}{7} ÷ 4 ＜ \frac{1}{7}$
$\frac{9}{8} = \frac{9}{8} ÷ 1$
$\frac{15}{34} ÷ \frac{15}{34} ＞ \frac{15}{34}$
$\frac{1}{7} ÷ 4 ＜ \frac{1}{7}$
$\frac{9}{8} = \frac{9}{8} ÷ 1$
$\frac{15}{34} ÷ \frac{15}{34} ＞ \frac{15}{34}$
(4)鸡的只数的$\frac{3}{4}$和兔的只数相等。等量关系是()的只数×$\frac{3}{4}$=()的只数。
答案
鸡
兔
兔
2. 我会算。
（1）直接写得数。
$0÷\frac{1}{3}=$ $\frac{5}{6}÷\frac{5}{12}=$ $\frac{9}{10}÷\frac{1}{3}=$ $\frac{2}{3}÷\frac{1}{9}=$ $\frac{3}{5}÷\frac{4}{5}=$
$\frac{8}{7}÷\frac{8}{7}=$ $\frac{5}{8}÷\frac{1}{2}=$ $\frac{8}{25}÷\frac{2}{5}=$ $1÷\frac{2}{3}=$ $1-\frac{7}{9}=$
（1）直接写得数。
$0÷\frac{1}{3}=$ $\frac{5}{6}÷\frac{5}{12}=$ $\frac{9}{10}÷\frac{1}{3}=$ $\frac{2}{3}÷\frac{1}{9}=$ $\frac{3}{5}÷\frac{4}{5}=$
$\frac{8}{7}÷\frac{8}{7}=$ $\frac{5}{8}÷\frac{1}{2}=$ $\frac{8}{25}÷\frac{2}{5}=$ $1÷\frac{2}{3}=$ $1-\frac{7}{9}=$
答案
$0÷\frac{1}{3}=0$
$\frac{5}{6}÷\frac{5}{12}=2$
$\frac{9}{10}÷\frac{1}{3}=\frac{27}{10}$
$\frac{2}{3}÷\frac{1}{9}=6$
$\frac{3}{5}÷\frac{4}{5}=\frac{3}{4}$
$\frac{8}{7}÷\frac{8}{7}=1$
$\frac{5}{8}÷\frac{1}{2}=\frac{5}{4}$
$\frac{8}{25}÷\frac{2}{5}=\frac{4}{5}$
$1÷\frac{2}{3}=\frac{3}{2}$
$1-\frac{7}{9}=\frac{2}{9}$
$\frac{5}{6}÷\frac{5}{12}=2$
$\frac{9}{10}÷\frac{1}{3}=\frac{27}{10}$
$\frac{2}{3}÷\frac{1}{9}=6$
$\frac{3}{5}÷\frac{4}{5}=\frac{3}{4}$
$\frac{8}{7}÷\frac{8}{7}=1$
$\frac{5}{8}÷\frac{1}{2}=\frac{5}{4}$
$\frac{8}{25}÷\frac{2}{5}=\frac{4}{5}$
$1÷\frac{2}{3}=\frac{3}{2}$
$1-\frac{7}{9}=\frac{2}{9}$
(2)脱式计算，能简算的要简算。
$25÷\frac{5}{9}$
$\frac{7}{16}÷\frac{7}{6}$
$\frac{1}{9}÷\frac{1}{15}$
$5÷\frac{15}{8}÷\frac{8}{15}$
$\frac{7}{6}÷14$
$(\frac{5}{8}+\frac{13}{16})÷\frac{13}{16}$
(3)解方程。
$\frac{2}{3}x=48$
$1.5x=22.5$
$\frac{7}{4}x=35$
$\frac{1}{3}x+5=25$
$25÷\frac{5}{9}$
$\frac{7}{16}÷\frac{7}{6}$
$\frac{1}{9}÷\frac{1}{15}$
$5÷\frac{15}{8}÷\frac{8}{15}$
$\frac{7}{6}÷14$
$(\frac{5}{8}+\frac{13}{16})÷\frac{13}{16}$
(3)解方程。
$\frac{2}{3}x=48$
$1.5x=22.5$
$\frac{7}{4}x=35$
$\frac{1}{3}x+5=25$
答案
(2) 脱式计算
$\begin{aligned}25÷\frac{5}{9}&=25×\frac{9}{5}\\&=45\end{aligned}$
$\begin{aligned}\frac{7}{16}÷\frac{7}{6}&=\frac{7}{16}×\frac{6}{7}\\&=\frac{3}{8}\end{aligned}$
$\begin{aligned}\frac{1}{9}÷\frac{1}{15}&=\frac{1}{9}×15\\&=\frac{5}{3}\end{aligned}$
$\begin{aligned}5÷\frac{15}{8}÷\frac{8}{15}&=5×\frac{8}{15}×\frac{15}{8}\\&=5×(\frac{8}{15}×\frac{15}{8})\\&=5×1\\&=5\end{aligned}$
$\begin{aligned}\frac{7}{6}÷14&=\frac{7}{6}×\frac{1}{14}\\&=\frac{1}{12}\end{aligned}$
$\begin{aligned}(\frac{5}{8}+\frac{13}{16})÷\frac{13}{16}&=(\frac{5}{8}+\frac{13}{16})×\frac{16}{13}\\&=\frac{5}{8}×\frac{16}{13}+\frac{13}{16}×\frac{16}{13}\\&=\frac{10}{13}+1\\&=\frac{23}{13}\end{aligned}$
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(3) 解方程
解：
$\begin{aligned}\frac{2}{3}x&=48\\x&=48÷\frac{2}{3}\\x&=72\end{aligned}$
解：
$\begin{aligned}1.5x&=22.5\\x&=22.5÷1.5\\x&=15\end{aligned}$
解：
$\begin{aligned}\frac{7}{4}x&=35\\x&=35÷\frac{7}{4}\\x&=20\end{aligned}$
解：
$\begin{aligned}\frac{1}{3}x+5&=25\\\frac{1}{3}x&=25-5\\\frac{1}{3}x&=20\\x&=60\end{aligned}$
$\begin{aligned}25÷\frac{5}{9}&=25×\frac{9}{5}\\&=45\end{aligned}$
$\begin{aligned}\frac{7}{16}÷\frac{7}{6}&=\frac{7}{16}×\frac{6}{7}\\&=\frac{3}{8}\end{aligned}$
$\begin{aligned}\frac{1}{9}÷\frac{1}{15}&=\frac{1}{9}×15\\&=\frac{5}{3}\end{aligned}$
$\begin{aligned}5÷\frac{15}{8}÷\frac{8}{15}&=5×\frac{8}{15}×\frac{15}{8}\\&=5×(\frac{8}{15}×\frac{15}{8})\\&=5×1\\&=5\end{aligned}$
$\begin{aligned}\frac{7}{6}÷14&=\frac{7}{6}×\frac{1}{14}\\&=\frac{1}{12}\end{aligned}$
$\begin{aligned}(\frac{5}{8}+\frac{13}{16})÷\frac{13}{16}&=(\frac{5}{8}+\frac{13}{16})×\frac{16}{13}\\&=\frac{5}{8}×\frac{16}{13}+\frac{13}{16}×\frac{16}{13}\\&=\frac{10}{13}+1\\&=\frac{23}{13}\end{aligned}$
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(3) 解方程
解：
$\begin{aligned}\frac{2}{3}x&=48\\x&=48÷\frac{2}{3}\\x&=72\end{aligned}$
解：
$\begin{aligned}1.5x&=22.5\\x&=22.5÷1.5\\x&=15\end{aligned}$
解：
$\begin{aligned}\frac{7}{4}x&=35\\x&=35÷\frac{7}{4}\\x&=20\end{aligned}$
解：
$\begin{aligned}\frac{1}{3}x+5&=25\\\frac{1}{3}x&=25-5\\\frac{1}{3}x&=20\\x&=60\end{aligned}$
