2. 用简便方法计算。
$0.75+\frac {1}{2}+\frac {1}{4}$ $3\frac {3}{8}-\frac {2}{7}-\frac {5}{7}$ $(\frac {1}{12}+\frac {1}{4})+(\frac {5}{12}+\frac {3}{4})$
$0.75+\frac {1}{2}+\frac {1}{4}$ $3\frac {3}{8}-\frac {2}{7}-\frac {5}{7}$ $(\frac {1}{12}+\frac {1}{4})+(\frac {5}{12}+\frac {3}{4})$
答案:
$0.75+\frac{1}{2}+\frac{1}{4}=1\frac{1}{2}$;$3\frac{3}{8}-\frac{2}{7}-\frac{5}{7}=2\frac{3}{8}$;$(\frac{1}{12}+\frac{1}{4})+(\frac{5}{12}+\frac{3}{4})=1\frac{1}{2}$。
3. 用递等式计算。
$\frac {5}{6}-\frac {1}{4}+\frac {1}{3}$ $\frac {7}{8}+\frac {1}{6}-\frac {5}{12}$ $(\frac {2}{3}+\frac {1}{4})+\frac {3}{5}$
$\frac {5}{6}-\frac {1}{4}+\frac {1}{3}$ $\frac {7}{8}+\frac {1}{6}-\frac {5}{12}$ $(\frac {2}{3}+\frac {1}{4})+\frac {3}{5}$
答案:
$\frac{5}{6}-\frac{1}{4}+\frac{1}{3}=\frac{11}{12}$;$\frac{7}{8}+\frac{1}{6}-\frac{5}{12}=\frac{5}{8}$;$(\frac{2}{3}+\frac{1}{4})+\frac{3}{5}=\frac{91}{60}$。
4. 解方程。
$\frac {3}{5}+x= \frac {9}{10}$ $\frac {7}{10}+x+\frac {1}{2}= \frac {15}{8}$ $\frac {4}{5}-x+\frac {1}{3}= \frac {4}{7}$
$\frac {3}{5}+x= \frac {9}{10}$ $\frac {7}{10}+x+\frac {1}{2}= \frac {15}{8}$ $\frac {4}{5}-x+\frac {1}{3}= \frac {4}{7}$
答案:
$x=\frac{3}{10}$;$x=\frac{27}{40}$;$x=\frac{59}{105}$
三、把下面的分数填入相应的圈里。
$\frac {1}{2}$ $\frac {3}{2}$ $\frac {6}{6}$ $\frac {14}{14}$ $\frac {23}{12}$ $\frac {39}{40}$ $\frac {37}{16}$

真分数
假分数
$\frac {1}{2}$ $\frac {3}{2}$ $\frac {6}{6}$ $\frac {14}{14}$ $\frac {23}{12}$ $\frac {39}{40}$ $\frac {37}{16}$
真分数
假分数
答案:
真分数$\frac {1}{2}$ $\frac {39}{40}$
假分数$\frac {3}{2}$ $\frac {6}{6}$ $\frac {14}{14}$ $\frac {23}{12}$ $\frac {37}{16}$
假分数$\frac {3}{2}$ $\frac {6}{6}$ $\frac {14}{14}$ $\frac {23}{12}$ $\frac {37}{16}$
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