1．计算下面各题．
| $\frac{3}{5}$×20= | $\frac{2}{7}$+$\frac{1}{3}$= | $\frac{1}{7}$×$\frac{2}{3}$= | $\frac{2}{9}$×18= |
| $\frac{3}{4}$-$\frac{1}{8}$= | $\frac{2}{9}$×4= | $\frac{4}{15}$×$\frac{5}{8}$= | $\frac{4}{5}$×$\frac{1}{8}$= |
20．$\frac{23}{6}$化成小数（保留三位小数）≈（ ）
| A． | 3.83 | B． | 3.833 | C． | 3.834 | D． | 3.830 |
15．在○里填上“＞”、“＜”或“=”号：
| $\frac{7}{12}$○$\frac{14}{24}$ | $\frac{9}{16}$○$\frac{11}{24}$ | $\frac{7}{8}$○$\frac{8}{9}$ |
| 4.75○4$\frac{3}{5}$ | $\frac{5}{8}$-$\frac{3}{8}$○$\frac{3}{4}$-$\frac{1}{4}$ | $\frac{1}{4}$+$\frac{5}{12}$○$\frac{1}{6}$+$\frac{1}{2}$ |
14．把 0.667、0.75、$\frac{1}{3}$、$\frac{2}{3}$、和0.6从小到大排列起来是$\frac{1}{3}$＜0.6＜$\frac{2}{3}$＜0.667＜0.75．
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