1. 填一填。
(1) 3 的倒数是( ),$\frac{2}{7}$的倒数是( ),1 的倒数是( )。
(2)( )的$\frac{2}{5}$是$\frac{7}{10}$,60 的$\frac{2}{5}$是( )。
(3)$36÷\frac{4}{5}=36×$( )=( ) $\frac{9}{16}÷\frac{3}{4}=$( )$◯$( )=( )
(1) 3 的倒数是( ),$\frac{2}{7}$的倒数是( ),1 的倒数是( )。
(2)( )的$\frac{2}{5}$是$\frac{7}{10}$,60 的$\frac{2}{5}$是( )。
(3)$36÷\frac{4}{5}=36×$( )=( ) $\frac{9}{16}÷\frac{3}{4}=$( )$◯$( )=( )
答案:
(1) $\frac{1}{3}$,$\frac{7}{2}$,1;
(2) $\frac{7}{4}$,24;
(3) $\frac{5}{4}$,45,$\frac{9}{16}$,$×$,$\frac{4}{3}$,$\frac{3}{4}$。
(1) $\frac{1}{3}$,$\frac{7}{2}$,1;
(2) $\frac{7}{4}$,24;
(3) $\frac{5}{4}$,45,$\frac{9}{16}$,$×$,$\frac{4}{3}$,$\frac{3}{4}$。
2. 算一算。
(1) 直接写出得数。
$12-\frac{1}{5}=$ $\frac{2}{7}×\frac{1}{2}=$ $\frac{1}{13}÷\frac{1}{13}=$ $\frac{5}{6}÷5=$
$\frac{2}{9}÷\frac{2}{5}=$ $15÷0.5=$ $\frac{7}{8}×0.4=$ $\frac{2}{13}×\frac{26}{5}=$
(2) 计算下面各题,能用简便算法的就用简便算法。
$27÷\frac{3}{7}÷\frac{9}{10}$ $\frac{2}{3}+\frac{2}{5}×\frac{15}{4}$ $\frac{1}{3}×\frac{3}{5}÷\frac{1}{3}×\frac{3}{5}$
$(\frac{2}{7}+\frac{3}{14})÷\frac{2}{21}$ $\frac{2}{11}×\frac{22}{5}÷\frac{2}{5}$ $\frac{7}{9}×\frac{2}{5}+\frac{3}{5}÷\frac{9}{7}$
(3) 解方程。
$x+\frac{4}{11}x=30$ $7x+4×\frac{5}{24}=2$ $\frac{4}{13}x÷\frac{2}{13}=20$
(1) 直接写出得数。
$12-\frac{1}{5}=$ $\frac{2}{7}×\frac{1}{2}=$ $\frac{1}{13}÷\frac{1}{13}=$ $\frac{5}{6}÷5=$
$\frac{2}{9}÷\frac{2}{5}=$ $15÷0.5=$ $\frac{7}{8}×0.4=$ $\frac{2}{13}×\frac{26}{5}=$
(2) 计算下面各题,能用简便算法的就用简便算法。
$27÷\frac{3}{7}÷\frac{9}{10}$ $\frac{2}{3}+\frac{2}{5}×\frac{15}{4}$ $\frac{1}{3}×\frac{3}{5}÷\frac{1}{3}×\frac{3}{5}$
$(\frac{2}{7}+\frac{3}{14})÷\frac{2}{21}$ $\frac{2}{11}×\frac{22}{5}÷\frac{2}{5}$ $\frac{7}{9}×\frac{2}{5}+\frac{3}{5}÷\frac{9}{7}$
(3) 解方程。
$x+\frac{4}{11}x=30$ $7x+4×\frac{5}{24}=2$ $\frac{4}{13}x÷\frac{2}{13}=20$
答案:
(1) $\frac{59}{5}$;$\frac{1}{7}$;1;$\frac{1}{6}$;$\frac{5}{9}$;30;$\frac{7}{20}$;$\frac{4}{5}$
(2) $27÷\frac{3}{7}÷\frac{9}{10}=27×\frac{7}{3}×\frac{10}{9}=70$;$\frac{2}{3}+\frac{2}{5}×\frac{15}{4}=\frac{2}{3}+\frac{3}{2}=\frac{13}{6}$;$\frac{1}{3}×\frac{3}{5}÷\frac{1}{3}×\frac{3}{5}=(\frac{1}{3}÷\frac{1}{3})×(\frac{3}{5}×\frac{3}{5})=\frac{9}{25}$;$(\frac{2}{7}+\frac{3}{14})÷\frac{2}{21}=(\frac{4}{14}+\frac{3}{14})×\frac{21}{2}=\frac{1}{2}×\frac{21}{2}=\frac{21}{4}$;$\frac{2}{11}×\frac{22}{5}÷\frac{2}{5}=\frac{2}{11}×\frac{22}{5}×\frac{5}{2}=2$;$\frac{7}{9}×\frac{2}{5}+\frac{3}{5}÷\frac{9}{7}=\frac{7}{9}×(\frac{2}{5}+\frac{3}{5})=\frac{7}{9}$
(3) $x+\frac{4}{11}x=30$解:$\frac{15}{11}x=30$,$x=30×\frac{11}{15}=22$;$7x+4×\frac{5}{24}=2$解:$7x+\frac{5}{6}=2$,$7x=\frac{7}{6}$,$x=\frac{1}{6}$;$\frac{4}{13}x÷\frac{2}{13}=20$解:$2x=20$,$x=10$
(1) $\frac{59}{5}$;$\frac{1}{7}$;1;$\frac{1}{6}$;$\frac{5}{9}$;30;$\frac{7}{20}$;$\frac{4}{5}$
(2) $27÷\frac{3}{7}÷\frac{9}{10}=27×\frac{7}{3}×\frac{10}{9}=70$;$\frac{2}{3}+\frac{2}{5}×\frac{15}{4}=\frac{2}{3}+\frac{3}{2}=\frac{13}{6}$;$\frac{1}{3}×\frac{3}{5}÷\frac{1}{3}×\frac{3}{5}=(\frac{1}{3}÷\frac{1}{3})×(\frac{3}{5}×\frac{3}{5})=\frac{9}{25}$;$(\frac{2}{7}+\frac{3}{14})÷\frac{2}{21}=(\frac{4}{14}+\frac{3}{14})×\frac{21}{2}=\frac{1}{2}×\frac{21}{2}=\frac{21}{4}$;$\frac{2}{11}×\frac{22}{5}÷\frac{2}{5}=\frac{2}{11}×\frac{22}{5}×\frac{5}{2}=2$;$\frac{7}{9}×\frac{2}{5}+\frac{3}{5}÷\frac{9}{7}=\frac{7}{9}×(\frac{2}{5}+\frac{3}{5})=\frac{7}{9}$
(3) $x+\frac{4}{11}x=30$解:$\frac{15}{11}x=30$,$x=30×\frac{11}{15}=22$;$7x+4×\frac{5}{24}=2$解:$7x+\frac{5}{6}=2$,$7x=\frac{7}{6}$,$x=\frac{1}{6}$;$\frac{4}{13}x÷\frac{2}{13}=20$解:$2x=20$,$x=10$
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