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1.下面各题算得对吗？正确的画“√”，错误的画“×”，并改正。
(1)$\frac{3}{5} - \frac{2}{5} × \frac{1}{2} = \frac{1}{5} × \frac{1}{2} = \frac{1}{10}$(
(2)$\frac{5}{7} × (1 - \frac{4}{7}) = \frac{5}{7} - \frac{4}{7} = \frac{1}{7}$(
(1)$\frac{3}{5} - \frac{2}{5} × \frac{1}{2} = \frac{1}{5} × \frac{1}{2} = \frac{1}{10}$(
×
)(2)$\frac{5}{7} × (1 - \frac{4}{7}) = \frac{5}{7} - \frac{4}{7} = \frac{1}{7}$(
×
)答案
1.(1) × 改正：$\frac{3}{5}-\frac{2}{5}×\frac{1}{2}=\frac{3}{5}-\frac{1}{5}=\frac{2}{5}$
1.(2) × 改正：$\frac{5}{7}×(1-\frac{4}{7})=\frac{5}{7}×\frac{3}{7}=\frac{15}{49}$
1.(2) × 改正：$\frac{5}{7}×(1-\frac{4}{7})=\frac{5}{7}×\frac{3}{7}=\frac{15}{49}$
2.运用运算律进行简便计算,将算式补充完整。
(1)$\frac{6}{5}×\frac{7}{8}×\frac{5}{6}=$ ○ ○
(2)$\frac{5}{12}×\frac{2}{3}+\frac{5}{12}×\frac{1}{3}=$ ○ ( ○ )
(3)$(\frac{5}{8}+\frac{3}{4})×12=$ ○ ○ ○
(4)$\frac{9}{10}-\frac{2}{3}×\frac{9}{10}=($ ○ ) ○
(1)$\frac{6}{5}×\frac{7}{8}×\frac{5}{6}=$ ○ ○
(2)$\frac{5}{12}×\frac{2}{3}+\frac{5}{12}×\frac{1}{3}=$ ○ ( ○ )
(3)$(\frac{5}{8}+\frac{3}{4})×12=$ ○ ○ ○
(4)$\frac{9}{10}-\frac{2}{3}×\frac{9}{10}=($ ○ ) ○
答案
2.(1) $\frac{6}{5} × \frac{5}{6} × \frac{7}{8}$
2.(2) $\frac{5}{12} × ( \frac{2}{3} + \frac{1}{3} )$
2.(3) $\frac{5}{8} × 12 + \frac{3}{4} × 12$
2.(4) $(1 - \frac{2}{3}) × \frac{9}{10}$
2.(2) $\frac{5}{12} × ( \frac{2}{3} + \frac{1}{3} )$
2.(3) $\frac{5}{8} × 12 + \frac{3}{4} × 12$
2.(4) $(1 - \frac{2}{3}) × \frac{9}{10}$
3.运用运算律进行简便计算,并说一说运用了什么运算律。
$\frac{33}{4}×\frac{3}{5}×\frac{12}{11}$
$(\frac{1}{6}+\frac{1}{8})×24$
$43×\frac{19}{42}$
$\frac{7}{20}×99+\frac{7}{20}$
$\frac{13}{5}×\frac{3}{13}-\frac{3}{13}×\frac{8}{5}$
$\frac{5}{12}×\frac{6}{25}×2.4×0.75$
$\frac{33}{4}×\frac{3}{5}×\frac{12}{11}$
$(\frac{1}{6}+\frac{1}{8})×24$
$43×\frac{19}{42}$
$\frac{7}{20}×99+\frac{7}{20}$
$\frac{13}{5}×\frac{3}{13}-\frac{3}{13}×\frac{8}{5}$
$\frac{5}{12}×\frac{6}{25}×2.4×0.75$
答案
（说一说略） $\frac{27}{5}$ 7 $19\frac{19}{42}$ 35 $\frac{3}{13}$ $\frac{9}{50}$
4.一台收割机1小时能收割$\frac{3}{4}$公顷小麦，5台收割机$\frac{2}{3}$小时能收割多少公顷小麦？
答案
4. $\frac{3}{4}×\frac{2}{3}×5=2.5$(公顷)
