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1. $\frac {9}{7}×30×\frac {7}{9}= \frac {9}{7}×(
\frac{7}{9}
)×(30
)= (30
)$答案
1. $\frac{7}{9}$ 30 30
2. $\frac {4}{5}×\frac {7}{10}+\frac {4}{5}×\frac {3}{10}= (
\frac{4}{5}
)×(\frac{7}{10}
+\frac{3}{10}
)= (\frac{4}{5}
)$答案
2. $\frac{4}{5}$ $\frac{7}{10}$ $\frac{3}{10}$ $\frac{4}{5}$
3. $(\frac {1}{4}+\frac {1}{6})×12= (
\frac{1}{4}
)×(12
)+(\frac{1}{6}
)×(12
)= (3
)+(2
)= (5
)$答案
3. $\frac{1}{4}$ 12 $\frac{1}{6}$ 12 3 2 5
二、用简便方法计算下面各题。
$\frac {13}{14}×\frac {5}{8}×\frac {28}{39}$ $(\frac {4}{5}+\frac {9}{10})×20$ $\frac {1}{8}×\frac {12}{13}×8×13$
$\frac {1}{6}×\frac {4}{7}+\frac {3}{7}×\frac {1}{6}$ $98×\frac {98}{99}$ $37×\frac {3}{4}+\frac {3}{4}×62+\frac {3}{4}$
$\frac {13}{14}×\frac {5}{8}×\frac {28}{39}$ $(\frac {4}{5}+\frac {9}{10})×20$ $\frac {1}{8}×\frac {12}{13}×8×13$
$\frac {1}{6}×\frac {4}{7}+\frac {3}{7}×\frac {1}{6}$ $98×\frac {98}{99}$ $37×\frac {3}{4}+\frac {3}{4}×62+\frac {3}{4}$
答案
二、$\frac{5}{12}$ 34 12 $\frac{1}{6}$ 97 $\frac{1}{99}$ 75
