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5. 计算下面各题。
- $5×1.25×\frac {2}{5}+0.78$ \n$(\frac {1}{2}-\frac {3}{8})÷\frac {3}{4}$
- $\frac {11}{12}÷\frac {2}{3}×\frac {2}{5}×\frac {3}{22}$ \n$\frac {5}{9}÷(\frac {4}{9}-\frac {2}{5}×\frac {5}{6})$
- $0.75÷\frac {3}{8}×(\frac {2}{3}-\frac {1}{6})$
- $\frac {1}{8}×[8÷(\frac {1}{8}×8)]$
- $5×1.25×\frac {2}{5}+0.78$ \n$(\frac {1}{2}-\frac {3}{8})÷\frac {3}{4}$
- $\frac {11}{12}÷\frac {2}{3}×\frac {2}{5}×\frac {3}{22}$ \n$\frac {5}{9}÷(\frac {4}{9}-\frac {2}{5}×\frac {5}{6})$
- $0.75÷\frac {3}{8}×(\frac {2}{3}-\frac {1}{6})$
- $\frac {1}{8}×[8÷(\frac {1}{8}×8)]$
答案
1. $5×1.25×\frac {2}{5}+0.78$
$=5×\frac{2}{5}×1.25+0.78$
$=2×1.25+0.78$
$=2.5+0.78$
$=3.28$
2. $(\frac {1}{2}-\frac {3}{8})÷\frac {3}{4}$
$=(\frac{4}{8}-\frac{3}{8})×\frac{4}{3}$
$=\frac{1}{8}×\frac{4}{3}$
$=\frac{1}{6}$
3. $\frac {11}{12}÷\frac {2}{3}×\frac {2}{5}×\frac {3}{22}$
$=\frac{11}{12}×\frac{3}{2}×\frac{2}{5}×\frac{3}{22}$
$=\frac{11×3×2×3}{12×2×5×22}$
$=\frac{3}{40}$
4. $\frac {5}{9}÷(\frac {4}{9}-\frac {2}{5}×\frac {5}{6})$
$=\frac{5}{9}÷(\frac{4}{9}-\frac{1}{3})$
$=\frac{5}{9}÷(\frac{4}{9}-\frac{3}{9})$
$=\frac{5}{9}÷\frac{1}{9}$
$=5$
5. $0.75÷\frac {3}{8}×(\frac {2}{3}-\frac {1}{6})$
$=\frac{3}{4}×\frac{8}{3}×(\frac{4}{6}-\frac{1}{6})$
$=2×\frac{1}{2}$
$=1$
6. $\frac {1}{8}×[8÷(\frac {1}{8}×8)]$
$=\frac{1}{8}×[8÷1]$
$=\frac{1}{8}×8$
$=1$
$=5×\frac{2}{5}×1.25+0.78$
$=2×1.25+0.78$
$=2.5+0.78$
$=3.28$
2. $(\frac {1}{2}-\frac {3}{8})÷\frac {3}{4}$
$=(\frac{4}{8}-\frac{3}{8})×\frac{4}{3}$
$=\frac{1}{8}×\frac{4}{3}$
$=\frac{1}{6}$
3. $\frac {11}{12}÷\frac {2}{3}×\frac {2}{5}×\frac {3}{22}$
$=\frac{11}{12}×\frac{3}{2}×\frac{2}{5}×\frac{3}{22}$
$=\frac{11×3×2×3}{12×2×5×22}$
$=\frac{3}{40}$
4. $\frac {5}{9}÷(\frac {4}{9}-\frac {2}{5}×\frac {5}{6})$
$=\frac{5}{9}÷(\frac{4}{9}-\frac{1}{3})$
$=\frac{5}{9}÷(\frac{4}{9}-\frac{3}{9})$
$=\frac{5}{9}÷\frac{1}{9}$
$=5$
5. $0.75÷\frac {3}{8}×(\frac {2}{3}-\frac {1}{6})$
$=\frac{3}{4}×\frac{8}{3}×(\frac{4}{6}-\frac{1}{6})$
$=2×\frac{1}{2}$
$=1$
6. $\frac {1}{8}×[8÷(\frac {1}{8}×8)]$
$=\frac{1}{8}×[8÷1]$
$=\frac{1}{8}×8$
$=1$
6. 用简便方法计算下面各题。\n$\frac {4}{15}÷7+\frac {11}{15}×\frac {1}{7}$ \n$(0.375+\frac {1}{27})×8+\frac {19}{27}$
- $(\frac {5}{6}-\frac {3}{8}+\frac {11}{24})÷\frac {1}{48}$ \n$\frac {4}{5}×\frac {9}{8}-\frac {1}{8}×0.8$ \n$(\frac {1}{3}-\frac {1}{4}+\frac {1}{6})×24$
- $\frac {14}{27}×75\% +\frac {13}{27}×\frac {3}{4}$
- $(\frac {5}{6}-\frac {3}{8}+\frac {11}{24})÷\frac {1}{48}$ \n$\frac {4}{5}×\frac {9}{8}-\frac {1}{8}×0.8$ \n$(\frac {1}{3}-\frac {1}{4}+\frac {1}{6})×24$
- $\frac {14}{27}×75\% +\frac {13}{27}×\frac {3}{4}$
答案
1. $\frac{4}{15}÷7+\frac{11}{15}×\frac{1}{7}$
$=\frac{4}{15}×\frac{1}{7}+\frac{11}{15}×\frac{1}{7}$
$=(\frac{4}{15}+\frac{11}{15})×\frac{1}{7}$
$=1×\frac{1}{7}$
$=\frac{1}{7}$
2. $(0.375+\frac{1}{27})×8+\frac{19}{27}$
$=\frac{3}{8}×8+\frac{1}{27}×8+\frac{19}{27}$
$=3+(\frac{8}{27}+\frac{19}{27})$
$=3+1$
$=4$
3. $(\frac{5}{6}-\frac{3}{8}+\frac{11}{24})÷\frac{1}{48}$
$=(\frac{5}{6}-\frac{3}{8}+\frac{11}{24})×48$
$=\frac{5}{6}×48-\frac{3}{8}×48+\frac{11}{24}×48$
$=40-18+22$
$=44$
4. $\frac{4}{5}×\frac{9}{8}-\frac{1}{8}×0.8$
$=\frac{4}{5}×\frac{9}{8}-\frac{1}{8}×\frac{4}{5}$
$=\frac{4}{5}×(\frac{9}{8}-\frac{1}{8})$
$=\frac{4}{5}×1$
$=\frac{4}{5}$
5. $(\frac{1}{3}-\frac{1}{4}+\frac{1}{6})×24$
$=\frac{1}{3}×24-\frac{1}{4}×24+\frac{1}{6}×24$
$=8-6+4$
$=6$
6. $\frac{14}{27}×75\%+\frac{13}{27}×\frac{3}{4}$
$=\frac{14}{27}×\frac{3}{4}+\frac{13}{27}×\frac{3}{4}$
$=(\frac{14}{27}+\frac{13}{27})×\frac{3}{4}$
$=1×\frac{3}{4}$
$=\frac{3}{4}$
$=\frac{4}{15}×\frac{1}{7}+\frac{11}{15}×\frac{1}{7}$
$=(\frac{4}{15}+\frac{11}{15})×\frac{1}{7}$
$=1×\frac{1}{7}$
$=\frac{1}{7}$
2. $(0.375+\frac{1}{27})×8+\frac{19}{27}$
$=\frac{3}{8}×8+\frac{1}{27}×8+\frac{19}{27}$
$=3+(\frac{8}{27}+\frac{19}{27})$
$=3+1$
$=4$
3. $(\frac{5}{6}-\frac{3}{8}+\frac{11}{24})÷\frac{1}{48}$
$=(\frac{5}{6}-\frac{3}{8}+\frac{11}{24})×48$
$=\frac{5}{6}×48-\frac{3}{8}×48+\frac{11}{24}×48$
$=40-18+22$
$=44$
4. $\frac{4}{5}×\frac{9}{8}-\frac{1}{8}×0.8$
$=\frac{4}{5}×\frac{9}{8}-\frac{1}{8}×\frac{4}{5}$
$=\frac{4}{5}×(\frac{9}{8}-\frac{1}{8})$
$=\frac{4}{5}×1$
$=\frac{4}{5}$
5. $(\frac{1}{3}-\frac{1}{4}+\frac{1}{6})×24$
$=\frac{1}{3}×24-\frac{1}{4}×24+\frac{1}{6}×24$
$=8-6+4$
$=6$
6. $\frac{14}{27}×75\%+\frac{13}{27}×\frac{3}{4}$
$=\frac{14}{27}×\frac{3}{4}+\frac{13}{27}×\frac{3}{4}$
$=(\frac{14}{27}+\frac{13}{27})×\frac{3}{4}$
$=1×\frac{3}{4}$
$=\frac{3}{4}$
