1.每日速算。
$2.4÷0.12=$
$10-\frac {3}{10}=$
$\frac {1}{5}+\frac {1}{7}=$
$3.6×20=$
$0.25×0.4=$
$2-1.02=$
$\frac {1}{2}+\frac {1}{5}=$
$2÷5=$
$2.4÷0.12=$
20
$10-\frac {3}{10}=$
$9\frac{7}{10}$
$\frac {1}{5}+\frac {1}{7}=$
$\frac{12}{35}$
$3.6×20=$
72
$0.25×0.4=$
0.1
$2-1.02=$
0.98
$\frac {1}{2}+\frac {1}{5}=$
$\frac{7}{10}$
$2÷5=$
$\frac{2}{5}$
答案:
20
$9\frac{7}{10}$
$\frac{12}{35}$
72
0.1
0.98
$\frac{7}{10}$
$\frac{2}{5}$
$9\frac{7}{10}$
$\frac{12}{35}$
72
0.1
0.98
$\frac{7}{10}$
$\frac{2}{5}$
2.计算下面各题,能简便计算的要用简便方法计算。
$\frac {7}{13}+\frac {1}{5}+\frac {6}{13}$ $\frac {5}{9}-(\frac {2}{9}+\frac {1}{3})$ $3-\frac {4}{9}-\frac {5}{9}$
$\frac {7}{8}-(\frac {3}{8}-\frac {1}{6})$ $\frac {4}{5}+(\frac {1}{3}-\frac {1}{5})$ $\frac {6}{13}+\frac {5}{12}+\frac {19}{12}+\frac {5}{13}$
$\frac {7}{13}+\frac {1}{5}+\frac {6}{13}$ $\frac {5}{9}-(\frac {2}{9}+\frac {1}{3})$ $3-\frac {4}{9}-\frac {5}{9}$
$\frac {7}{8}-(\frac {3}{8}-\frac {1}{6})$ $\frac {4}{5}+(\frac {1}{3}-\frac {1}{5})$ $\frac {6}{13}+\frac {5}{12}+\frac {19}{12}+\frac {5}{13}$
答案:
$\frac{7}{13}+\frac{1}{5}+\frac{6}{13}$
$=(\frac{7}{13}+\frac{6}{13})+\frac{1}{5}$
$=1+\frac{1}{5}$
$=1\frac{1}{5}$
$\frac{5}{9}-(\frac{2}{9}+\frac{1}{3})$
$=\frac{5}{9}-\frac{2}{9}-\frac{3}{9}$
$=0$
$3-\frac{4}{9}-\frac{5}{9}$
$=3-(\frac{4}{9}+\frac{5}{9})$
$=3-1$
$=2$
$\frac{7}{8}-(\frac{3}{8}-\frac{1}{6})$
$=\frac{7}{8}-\frac{3}{8}+\frac{1}{6}$
$=\frac{4}{8}+\frac{1}{6}$
$=\frac{1}{2}+\frac{1}{6}$
$=\frac{2}{3}$
$\frac{4}{5}+(\frac{1}{3}-\frac{1}{5})$
$=\frac{4}{5}-\frac{1}{5}+\frac{1}{3}$
$=\frac{3}{5}+\frac{1}{3}$
$=\frac{14}{15}$
$\frac{6}{13}+\frac{5}{12}+\frac{19}{12}+\frac{5}{13}$
$=(\frac{6}{13}+\frac{5}{13})+(\frac{5}{12}+\frac{19}{12})$
$=\frac{11}{13}+2$
$=2\frac{11}{13}$
$=(\frac{7}{13}+\frac{6}{13})+\frac{1}{5}$
$=1+\frac{1}{5}$
$=1\frac{1}{5}$
$\frac{5}{9}-(\frac{2}{9}+\frac{1}{3})$
$=\frac{5}{9}-\frac{2}{9}-\frac{3}{9}$
$=0$
$3-\frac{4}{9}-\frac{5}{9}$
$=3-(\frac{4}{9}+\frac{5}{9})$
$=3-1$
$=2$
$\frac{7}{8}-(\frac{3}{8}-\frac{1}{6})$
$=\frac{7}{8}-\frac{3}{8}+\frac{1}{6}$
$=\frac{4}{8}+\frac{1}{6}$
$=\frac{1}{2}+\frac{1}{6}$
$=\frac{2}{3}$
$\frac{4}{5}+(\frac{1}{3}-\frac{1}{5})$
$=\frac{4}{5}-\frac{1}{5}+\frac{1}{3}$
$=\frac{3}{5}+\frac{1}{3}$
$=\frac{14}{15}$
$\frac{6}{13}+\frac{5}{12}+\frac{19}{12}+\frac{5}{13}$
$=(\frac{6}{13}+\frac{5}{13})+(\frac{5}{12}+\frac{19}{12})$
$=\frac{11}{13}+2$
$=2\frac{11}{13}$
3.参考下面第一幅图,在第二幅图上写出长方体的一个顶点、一个面和一条棱。

答案:
3. 答案不唯一,例如
3. 答案不唯一,例如
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