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三、我会算。
$\frac{5}{7}÷\frac{3}{4}×\frac{3}{2}$ $3-\frac{2}{5}÷\frac{3}{5}$ $\frac{8}{15}÷(\frac{8}{9}+\frac{2}{3})$
$\frac{2}{15}÷\frac{2}{5}+\frac{1}{4}$ $\frac{4}{9}÷\frac{8}{3}+\frac{3}{8}÷\frac{5}{9}$ $\frac{4}{9}÷[\frac{4}{5}-(\frac{1}{5}+\frac{1}{3})]$
$\frac{5}{7}÷\frac{3}{4}×\frac{3}{2}$ $3-\frac{2}{5}÷\frac{3}{5}$ $\frac{8}{15}÷(\frac{8}{9}+\frac{2}{3})$
$\frac{2}{15}÷\frac{2}{5}+\frac{1}{4}$ $\frac{4}{9}÷\frac{8}{3}+\frac{3}{8}÷\frac{5}{9}$ $\frac{4}{9}÷[\frac{4}{5}-(\frac{1}{5}+\frac{1}{3})]$
答案
$\frac{10}{7}$ $\frac{7}{3}$ $\frac{12}{35}$ $\frac{7}{12}$ $\frac{101}{120}$ $\frac{5}{3}$
解析
$\frac{5}{7}÷\frac{3}{4}×\frac{3}{2}=\frac{5}{7}×\frac{4}{3}×\frac{3}{2}=\frac{5}{7}×2=\frac{10}{7}$
$3-\frac{2}{5}÷\frac{3}{5}=3-\frac{2}{5}×\frac{5}{3}=3-\frac{2}{3}=\frac{7}{3}$
$\frac{8}{15}÷(\frac{8}{9}+\frac{2}{3})=\frac{8}{15}÷(\frac{8}{9}+\frac{6}{9})=\frac{8}{15}÷\frac{14}{9}=\frac{8}{15}×\frac{9}{14}=\frac{12}{35}$
$\frac{2}{15}÷\frac{2}{5}+\frac{1}{4}=\frac{2}{15}×\frac{5}{2}+\frac{1}{4}=\frac{1}{3}+\frac{1}{4}=\frac{7}{12}$
$\frac{4}{9}÷\frac{8}{3}+\frac{3}{8}÷\frac{5}{9}=\frac{4}{9}×\frac{3}{8}+\frac{3}{8}×\frac{9}{5}=\frac{1}{6}+\frac{27}{40}=\frac{20}{120}+\frac{81}{120}=\frac{101}{120}$
$\frac{4}{9}÷[\frac{4}{5}-(\frac{1}{5}+\frac{1}{3})]=\frac{4}{9}÷[\frac{4}{5}-\frac{1}{5}-\frac{1}{3}]=\frac{4}{9}÷[\frac{3}{5}-\frac{1}{3}]=\frac{4}{9}÷[\frac{9}{15}-\frac{5}{15}]=\frac{4}{9}÷\frac{4}{15}=\frac{4}{9}×\frac{15}{4}=\frac{5}{3}$
$3-\frac{2}{5}÷\frac{3}{5}=3-\frac{2}{5}×\frac{5}{3}=3-\frac{2}{3}=\frac{7}{3}$
$\frac{8}{15}÷(\frac{8}{9}+\frac{2}{3})=\frac{8}{15}÷(\frac{8}{9}+\frac{6}{9})=\frac{8}{15}÷\frac{14}{9}=\frac{8}{15}×\frac{9}{14}=\frac{12}{35}$
$\frac{2}{15}÷\frac{2}{5}+\frac{1}{4}=\frac{2}{15}×\frac{5}{2}+\frac{1}{4}=\frac{1}{3}+\frac{1}{4}=\frac{7}{12}$
$\frac{4}{9}÷\frac{8}{3}+\frac{3}{8}÷\frac{5}{9}=\frac{4}{9}×\frac{3}{8}+\frac{3}{8}×\frac{9}{5}=\frac{1}{6}+\frac{27}{40}=\frac{20}{120}+\frac{81}{120}=\frac{101}{120}$
$\frac{4}{9}÷[\frac{4}{5}-(\frac{1}{5}+\frac{1}{3})]=\frac{4}{9}÷[\frac{4}{5}-\frac{1}{5}-\frac{1}{3}]=\frac{4}{9}÷[\frac{3}{5}-\frac{1}{3}]=\frac{4}{9}÷[\frac{9}{15}-\frac{5}{15}]=\frac{4}{9}÷\frac{4}{15}=\frac{4}{9}×\frac{15}{4}=\frac{5}{3}$
四、我会解方程。
$x÷\frac{3}{2}= \frac{9}{40}$ $7x÷\frac{1}{10}= \frac{3}{5}$ $(\frac{2}{3}-\frac{1}{2})x= \frac{1}{3}$
$x÷\frac{3}{2}= \frac{9}{40}$ $7x÷\frac{1}{10}= \frac{3}{5}$ $(\frac{2}{3}-\frac{1}{2})x= \frac{1}{3}$
答案
$x=\frac{27}{80}$ $x=\frac{3}{350}$ $x=2$
解析
解：$x÷\frac{3}{2}=\frac{9}{40}$
$x=\frac{9}{40}×\frac{3}{2}$
$x=\frac{27}{80}$
解：$7x÷\frac{1}{10}=\frac{3}{5}$
$7x=\frac{3}{5}×\frac{1}{10}$
$7x=\frac{3}{50}$
$x=\frac{3}{50}÷7$
$x=\frac{3}{350}$
解：$(\frac{2}{3}-\frac{1}{2})x=\frac{1}{3}$
$(\frac{4}{6}-\frac{3}{6})x=\frac{1}{3}$
$\frac{1}{6}x=\frac{1}{3}$
$x=\frac{1}{3}÷\frac{1}{6}$
$x=2$
$x=\frac{9}{40}×\frac{3}{2}$
$x=\frac{27}{80}$
解：$7x÷\frac{1}{10}=\frac{3}{5}$
$7x=\frac{3}{5}×\frac{1}{10}$
$7x=\frac{3}{50}$
$x=\frac{3}{50}÷7$
$x=\frac{3}{350}$
解：$(\frac{2}{3}-\frac{1}{2})x=\frac{1}{3}$
$(\frac{4}{6}-\frac{3}{6})x=\frac{1}{3}$
$\frac{1}{6}x=\frac{1}{3}$
$x=\frac{1}{3}÷\frac{1}{6}$
$x=2$
1. 三角形的面积为$\frac{3}{8}m^2$,底为$\frac{4}{5}m$,高为多少米？
答案
$\frac{3}{8}× 2÷ \frac{4}{5}=\frac{15}{16}(m)$
解析
$\frac{3}{8} × 2 ÷ \frac{4}{5} = \frac{3}{4} ÷ \frac{4}{5} = \frac{3}{4} × \frac{5}{4} = \frac{15}{16}(m)$
2. 一辆汽车行驶$\frac{3}{2}km耗油\frac{9}{50}L$。
(1)平均1L汽油可以行驶多少千米？ (2)平均行驶1km要耗油多少升？
(1)平均1L汽油可以行驶多少千米？ (2)平均行驶1km要耗油多少升？
答案
(1)$\frac{3}{2}÷ \frac{9}{50}=\frac{25}{3}(km)$
(2)$\frac{9}{50}÷ \frac{3}{2}=\frac{3}{25}(L)$
