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二、计算下面各题,怎样简便就怎样计算。
$\frac {8}{25}÷7+\frac {1}{7}×\frac {6}{25}$ $\frac {1}{2}×\frac {2}{5}+\frac {9}{10}÷\frac {9}{20}$ $8000-8000×(1-14\% )$
$\frac {2}{9}+\frac {1}{2}÷\frac {4}{5}+\frac {3}{8}$ $(\frac {1}{2}+\frac {2}{3}+\frac {3}{4})×24$ $400÷(1+25\% )-200$
$\frac {7}{9}÷\frac {11}{5}+\frac {2}{9}×\frac {5}{11}$ $\frac {1}{18}×22×9×\frac {3}{11}$ $240×\frac {7}{6}×\frac {13}{14}$
$\frac {2}{3}×(1÷\frac {3}{4}-1)$ $(\frac {4}{9}+\frac {2}{15})×15×9$ $10000×(1-20\% )×90\% $
$(\frac {5}{8}-\frac {1}{4})×(\frac {8}{9}÷\frac {4}{15})$ $\frac {2}{7}÷[\frac {5}{6}×(\frac {4}{5}-\frac {2}{3})]$ $480×\frac {5}{6}÷\frac {4}{5}-480$
$\frac {8}{25}÷7+\frac {1}{7}×\frac {6}{25}$ $\frac {1}{2}×\frac {2}{5}+\frac {9}{10}÷\frac {9}{20}$ $8000-8000×(1-14\% )$
$\frac {2}{9}+\frac {1}{2}÷\frac {4}{5}+\frac {3}{8}$ $(\frac {1}{2}+\frac {2}{3}+\frac {3}{4})×24$ $400÷(1+25\% )-200$
$\frac {7}{9}÷\frac {11}{5}+\frac {2}{9}×\frac {5}{11}$ $\frac {1}{18}×22×9×\frac {3}{11}$ $240×\frac {7}{6}×\frac {13}{14}$
$\frac {2}{3}×(1÷\frac {3}{4}-1)$ $(\frac {4}{9}+\frac {2}{15})×15×9$ $10000×(1-20\% )×90\% $
$(\frac {5}{8}-\frac {1}{4})×(\frac {8}{9}÷\frac {4}{15})$ $\frac {2}{7}÷[\frac {5}{6}×(\frac {4}{5}-\frac {2}{3})]$ $480×\frac {5}{6}÷\frac {4}{5}-480$
答案
$\frac{2}{25}$ $2\frac{1}{5}$ 1120 $1\frac{2}{9}$ 46 120 $\frac{5}{11}$ 3 260 $\frac{2}{9}$ 78 7200 $\frac{5}{4}$ $\frac{18}{7}$ 20
解析
1. $\frac{8}{25}÷7+\frac{1}{7}×\frac{6}{25}$
解：$=\frac{8}{25}×\frac{1}{7}+\frac{1}{7}×\frac{6}{25}$
$=(\frac{8}{25}+\frac{6}{25})×\frac{1}{7}$
$=\frac{14}{25}×\frac{1}{7}$
$=\frac{2}{25}$
2. $\frac{1}{2}×\frac{2}{5}+\frac{9}{10}÷\frac{9}{20}$
解：$=\frac{1}{5}+\frac{9}{10}×\frac{20}{9}$
$=\frac{1}{5}+2$
$=2\frac{1}{5}$
3. $8000 - 8000×(1 - 14\%)$
解：$=8000 - 8000×86\%$
$=8000 - 6880$
$=1120$
4. $\frac{2}{9}+\frac{1}{2}÷\frac{4}{5}+\frac{3}{8}$
解：$=\frac{2}{9}+\frac{1}{2}×\frac{5}{4}+\frac{3}{8}$
$=\frac{2}{9}+\frac{5}{8}+\frac{3}{8}$
$=\frac{2}{9}+(\frac{5}{8}+\frac{3}{8})$
$=\frac{2}{9}+1$
$=1\frac{2}{9}$
5. $(\frac{1}{2}+\frac{2}{3}+\frac{3}{4})×24$
解：$=\frac{1}{2}×24+\frac{2}{3}×24+\frac{3}{4}×24$
$=12 + 16 + 18$
$=46$
6. $400÷(1 + 25\%) - 200$
解：$=400÷1.25 - 200$
$=320 - 200$
$=120$
7. $\frac{7}{9}÷\frac{11}{5}+\frac{2}{9}×\frac{5}{11}$
解：$=\frac{7}{9}×\frac{5}{11}+\frac{2}{9}×\frac{5}{11}$
$=(\frac{7}{9}+\frac{2}{9})×\frac{5}{11}$
$=1×\frac{5}{11}$
$=\frac{5}{11}$
8. $\frac{1}{18}×22×9×\frac{3}{11}$
解：$=(\frac{1}{18}×9)×(22×\frac{3}{11})$
$=\frac{1}{2}×6$
$=3$
9. $240×\frac{7}{6}×\frac{13}{14}$
解：$=280×\frac{13}{14}$
$=260$
10. $\frac{2}{3}×(1÷\frac{3}{4}-1)$
解：$=\frac{2}{3}×(\frac{4}{3}-1)$
$=\frac{2}{3}×\frac{1}{3}$
$=\frac{2}{9}$
11. $(\frac{4}{9}+\frac{2}{15})×15×9$
解：$=\frac{4}{9}×15×9+\frac{2}{15}×15×9$
$=60 + 18$
$=78$
12. $10000×(1 - 20\%)×90\%$
解：$=10000×0.8×0.9$
$=8000×0.9$
$=7200$
13. $(\frac{5}{8}-\frac{1}{4})×(\frac{8}{9}÷\frac{4}{15})$
解：$=(\frac{5}{8}-\frac{2}{8})×(\frac{8}{9}×\frac{15}{4})$
$=\frac{3}{8}×\frac{10}{3}$
$=\frac{5}{4}$
14. $\frac{2}{7}÷[\frac{5}{6}×(\frac{4}{5}-\frac{2}{3})]$
解：$=\frac{2}{7}÷[\frac{5}{6}×(\frac{12}{15}-\frac{10}{15})]$
$=\frac{2}{7}÷[\frac{5}{6}×\frac{2}{15}]$
$=\frac{2}{7}÷\frac{1}{9}$
$=\frac{2}{7}×9$
$=\frac{18}{7}$
15. $480×\frac{5}{6}÷\frac{4}{5}-480$
解：$=400×\frac{5}{4}-480$
$=500 - 480$
$=20$
解：$=\frac{8}{25}×\frac{1}{7}+\frac{1}{7}×\frac{6}{25}$
$=(\frac{8}{25}+\frac{6}{25})×\frac{1}{7}$
$=\frac{14}{25}×\frac{1}{7}$
$=\frac{2}{25}$
2. $\frac{1}{2}×\frac{2}{5}+\frac{9}{10}÷\frac{9}{20}$
解：$=\frac{1}{5}+\frac{9}{10}×\frac{20}{9}$
$=\frac{1}{5}+2$
$=2\frac{1}{5}$
3. $8000 - 8000×(1 - 14\%)$
解：$=8000 - 8000×86\%$
$=8000 - 6880$
$=1120$
4. $\frac{2}{9}+\frac{1}{2}÷\frac{4}{5}+\frac{3}{8}$
解：$=\frac{2}{9}+\frac{1}{2}×\frac{5}{4}+\frac{3}{8}$
$=\frac{2}{9}+\frac{5}{8}+\frac{3}{8}$
$=\frac{2}{9}+(\frac{5}{8}+\frac{3}{8})$
$=\frac{2}{9}+1$
$=1\frac{2}{9}$
5. $(\frac{1}{2}+\frac{2}{3}+\frac{3}{4})×24$
解：$=\frac{1}{2}×24+\frac{2}{3}×24+\frac{3}{4}×24$
$=12 + 16 + 18$
$=46$
6. $400÷(1 + 25\%) - 200$
解：$=400÷1.25 - 200$
$=320 - 200$
$=120$
7. $\frac{7}{9}÷\frac{11}{5}+\frac{2}{9}×\frac{5}{11}$
解：$=\frac{7}{9}×\frac{5}{11}+\frac{2}{9}×\frac{5}{11}$
$=(\frac{7}{9}+\frac{2}{9})×\frac{5}{11}$
$=1×\frac{5}{11}$
$=\frac{5}{11}$
8. $\frac{1}{18}×22×9×\frac{3}{11}$
解：$=(\frac{1}{18}×9)×(22×\frac{3}{11})$
$=\frac{1}{2}×6$
$=3$
9. $240×\frac{7}{6}×\frac{13}{14}$
解：$=280×\frac{13}{14}$
$=260$
10. $\frac{2}{3}×(1÷\frac{3}{4}-1)$
解：$=\frac{2}{3}×(\frac{4}{3}-1)$
$=\frac{2}{3}×\frac{1}{3}$
$=\frac{2}{9}$
11. $(\frac{4}{9}+\frac{2}{15})×15×9$
解：$=\frac{4}{9}×15×9+\frac{2}{15}×15×9$
$=60 + 18$
$=78$
12. $10000×(1 - 20\%)×90\%$
解：$=10000×0.8×0.9$
$=8000×0.9$
$=7200$
13. $(\frac{5}{8}-\frac{1}{4})×(\frac{8}{9}÷\frac{4}{15})$
解：$=(\frac{5}{8}-\frac{2}{8})×(\frac{8}{9}×\frac{15}{4})$
$=\frac{3}{8}×\frac{10}{3}$
$=\frac{5}{4}$
14. $\frac{2}{7}÷[\frac{5}{6}×(\frac{4}{5}-\frac{2}{3})]$
解：$=\frac{2}{7}÷[\frac{5}{6}×(\frac{12}{15}-\frac{10}{15})]$
$=\frac{2}{7}÷[\frac{5}{6}×\frac{2}{15}]$
$=\frac{2}{7}÷\frac{1}{9}$
$=\frac{2}{7}×9$
$=\frac{18}{7}$
15. $480×\frac{5}{6}÷\frac{4}{5}-480$
解：$=400×\frac{5}{4}-480$
$=500 - 480$
$=20$
